diff --git a/exercises/B-hello-world/exercise.js b/exercises/B-hello-world/exercise.js
index b179ee953..2a7b53565 100644
--- a/exercises/B-hello-world/exercise.js
+++ b/exercises/B-hello-world/exercise.js
@@ -1 +1,2 @@
-console.log("Hello world");
+console.log("Hello World. I just started learning JavaScript!");
+console.log(123);
\ No newline at end of file
diff --git a/exercises/C-variables/exercise.js b/exercises/C-variables/exercise.js
index a6bbb9786..6a1175bba 100644
--- a/exercises/C-variables/exercise.js
+++ b/exercises/C-variables/exercise.js
@@ -1,3 +1,5 @@
 // Start by creating a variable `greeting`
-
+var greeting = "Hello world";
 console.log(greeting);
+console.log(greeting);
+console.log(greeting);
\ No newline at end of file
diff --git a/exercises/D-strings/exercise.js b/exercises/D-strings/exercise.js
index 2cffa6a81..d2fa02cc3 100644
--- a/exercises/D-strings/exercise.js
+++ b/exercises/D-strings/exercise.js
@@ -1,3 +1,5 @@
 // Start by creating a variable `message`
+var message = "This is a string";
 
 console.log(message);
+console.log(typeof message);
\ No newline at end of file
diff --git a/exercises/E-strings-concatenation/exercise.js b/exercises/E-strings-concatenation/exercise.js
index 2cffa6a81..1feb30046 100644
--- a/exercises/E-strings-concatenation/exercise.js
+++ b/exercises/E-strings-concatenation/exercise.js
@@ -1,3 +1,6 @@
 // Start by creating a variable `message`
+var greetingStart = "Hello, my name is ";
+var name = "Hassan";
 
-console.log(message);
+var greeting = greetingStart + name;
+console.log(greeting);
\ No newline at end of file
diff --git a/exercises/F-strings-methods/exercise.js b/exercises/F-strings-methods/exercise.js
index 2cffa6a81..5f3e3ab25 100644
--- a/exercises/F-strings-methods/exercise.js
+++ b/exercises/F-strings-methods/exercise.js
@@ -1,3 +1,3 @@
 // Start by creating a variable `message`
-
-console.log(message);
+let message = "My name is Hassan and my name is ";
+console.log(message + message.length + " characters long");
\ No newline at end of file
diff --git a/exercises/F-strings-methods/exercise2.js b/exercises/F-strings-methods/exercise2.js
index b4b46943d..7e11736ce 100644
--- a/exercises/F-strings-methods/exercise2.js
+++ b/exercises/F-strings-methods/exercise2.js
@@ -1,3 +1,3 @@
 const name = " Daniel  ";
 
-console.log(message);
+console.log(name.trim());
\ No newline at end of file
diff --git a/exercises/G-numbers/exercise.js b/exercises/G-numbers/exercise.js
index 49e7bc00b..7023eae07 100644
--- a/exercises/G-numbers/exercise.js
+++ b/exercises/G-numbers/exercise.js
@@ -1 +1,4 @@
 // Start by creating a variables `numberOfStudents` and `numberOfMentors`
+let numberOfStudents = 5;
+let numberOfMentors = 1;
+console.log(numberOfStudents + numberOfMentors);
\ No newline at end of file
diff --git a/exercises/I-floats/exercise.js b/exercises/I-floats/exercise.js
index a5bbcd852..5e38b1b22 100644
--- a/exercises/I-floats/exercise.js
+++ b/exercises/I-floats/exercise.js
@@ -1,2 +1,9 @@
-var numberOfStudents = 15;
-var numberOfMentors = 8;
+let numberOfStudents = 15;
+let numberOfMentors = 8;
+let total = numberOfStudents + numberOfMentors;
+
+let pStudens = Math.round(numberOfStudents * 100 / total);
+let pMentor = Math.round(numberOfMentors * 100 / total);
+
+console.log("Percentage students: " + pStudens + "%");
+console.log("Percentage mentors: " + pMentor + "%");
\ No newline at end of file
diff --git a/exercises/J-functions/exercise.js b/exercises/J-functions/exercise.js
index 0ae5850e5..d367b349f 100644
--- a/exercises/J-functions/exercise.js
+++ b/exercises/J-functions/exercise.js
@@ -1,7 +1,9 @@
 function halve(number) {
-  // complete the function here
+    return number / 2;
 }
 
 var result = halve(12);
+var result2 = halve(120);
 
 console.log(result);
+console.log(result2);
\ No newline at end of file
diff --git a/exercises/J-functions/exercise2.js b/exercises/J-functions/exercise2.js
index 82ef5e780..ba12fd1e4 100644
--- a/exercises/J-functions/exercise2.js
+++ b/exercises/J-functions/exercise2.js
@@ -1,7 +1,7 @@
 function triple(number) {
-  // complete function here
+    return number * 3;
 }
 
 var result = triple(12);
 
-console.log(result);
+console.log(result);
\ No newline at end of file
diff --git a/exercises/K-functions-parameters/exercise.js b/exercises/K-functions-parameters/exercise.js
index 8d5db5e69..440d507d3 100644
--- a/exercises/K-functions-parameters/exercise.js
+++ b/exercises/K-functions-parameters/exercise.js
@@ -1,9 +1,9 @@
 // Complete the function so that it takes input parameters
-function multiply() {
-  // Calculate the result of the function and return it
+function multiply(x, y) {
+    return x * y;
 }
 
 // Assign the result of calling the function the variable `result`
 var result = multiply(3, 4);
 
-console.log(result);
+console.log(result);
\ No newline at end of file
diff --git a/exercises/K-functions-parameters/exercise2.js b/exercises/K-functions-parameters/exercise2.js
index db7a8904b..6d980c574 100644
--- a/exercises/K-functions-parameters/exercise2.js
+++ b/exercises/K-functions-parameters/exercise2.js
@@ -1,5 +1,8 @@
 // Declare your function first
+function divide(x, y) {
+    return x / y;
+}
 
 var result = divide(3, 4);
 
-console.log(result);
+console.log(result);
\ No newline at end of file
diff --git a/exercises/K-functions-parameters/exercise3.js b/exercises/K-functions-parameters/exercise3.js
index 537e9f4ec..6f53c724a 100644
--- a/exercises/K-functions-parameters/exercise3.js
+++ b/exercises/K-functions-parameters/exercise3.js
@@ -1,5 +1,8 @@
 // Write your function here
+function createGreeting(name) {
+    return "Hello, my name is " + name;
+}
 
 var greeting = createGreeting("Daniel");
 
-console.log(greeting);
+console.log(greeting);
\ No newline at end of file
diff --git a/exercises/K-functions-parameters/exercise4.js b/exercises/K-functions-parameters/exercise4.js
index 7ab44589e..9696da0af 100644
--- a/exercises/K-functions-parameters/exercise4.js
+++ b/exercises/K-functions-parameters/exercise4.js
@@ -1,5 +1,7 @@
-// Declare your function first
+function add(x, y) {
+    return x + y;
+}
 
-// Call the function and assign to a variable `sum`
+var sum = add(13, 124);
 
-console.log(sum);
+console.log(sum);
\ No newline at end of file
diff --git a/exercises/K-functions-parameters/exercise5.js b/exercises/K-functions-parameters/exercise5.js
index 7c5bcd605..7d7dc70a5 100644
--- a/exercises/K-functions-parameters/exercise5.js
+++ b/exercises/K-functions-parameters/exercise5.js
@@ -1,5 +1,8 @@
 // Declare your function here
-
+function createLongGreeting(name, age) {
+    return `Hello, my name is ${name} and I'm ${age} years old`;
+}
 const greeting = createLongGreeting("Daniel", 30);
 
-console.log(greeting);
+
+console.log(greeting);
\ No newline at end of file
diff --git a/exercises/L-functions-nested/exercise.js b/exercises/L-functions-nested/exercise.js
index a5d377442..fa4d08ef3 100644
--- a/exercises/L-functions-nested/exercise.js
+++ b/exercises/L-functions-nested/exercise.js
@@ -3,3 +3,17 @@ var mentor2 = "Irina";
 var mentor3 = "Mimi";
 var mentor4 = "Rob";
 var mentor5 = "Yohannes";
+
+function upperCase(name) {
+    return name.toUpperCase();
+}
+
+function greeting(name) {
+    return upperCase("Hello") + " " + upperCase(name);
+}
+
+console.log(greeting(mentor1));
+console.log(greeting(mentor2));
+console.log(greeting(mentor3));
+console.log(greeting(mentor4));
+console.log(greeting(mentor5));
\ No newline at end of file
diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index a10cc9ac2..0e1e381bd 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,16 +1,17 @@
 // There are syntax errors in this code - can you fix it to pass the tests?
 
-function addNumbers(a b c) {
-  return a + b + c;
+function addNumbers(a, b, c) {
+    return a + b + c;
 }
 
-function introduceMe(name, age)
-  return "Hello, my name is " + name "and I am " age + "years old";
+function introduceMe(name, age) {
+    return "Hello, my name is " + name + " and I am " + age + " years old";
+}
 
 function getTotal(a, b) {
-  total = a ++ b;
+    total = a + +b;
 
-  return "The total is total";
+    return "The total is " + total;
 }
 
 /* 
@@ -26,15 +27,15 @@ To run the tests for just this one file, type `npm test -- --testPathPattern 1-s
 */
 
 test("addNumbers adds numbers correctly", () => {
-  expect(addNumbers(3, 4, 6)).toEqual(13);
+    expect(addNumbers(3, 4, 6)).toEqual(13);
 });
 
 test("introduceMe function returns the correct string", () => {
-  expect(introduceMe("Sonjide", 27)).toEqual(
-    "Hello, my name is Sonjide and I am 27 years old"
-  );
+    expect(introduceMe("Sonjide", 27)).toEqual(
+        "Hello, my name is Sonjide and I am 27 years old"
+    );
 });
 
 test("getTotal returns a string describing the total", () => {
-  expect(getTotal(23, 5)).toEqual("The total is 28");
-});
+    expect(getTotal(23, 5)).toEqual("The total is 28");
+});
\ No newline at end of file
diff --git a/mandatory/2-logic-error.js b/mandatory/2-logic-error.js
index 9cca7603b..a9632a6ff 100644
--- a/mandatory/2-logic-error.js
+++ b/mandatory/2-logic-error.js
@@ -1,16 +1,15 @@
 // The syntax for this function is valid but it has an error, find it and fix it.
 
 function trimWord(word) {
-  return wordtrim();
+    return word.trim();
 }
 
 function getStringLength(word) {
-  return "word".length();
+    return word.length;
 }
 
 function multiply(a, b, c) {
-  a * b * c;
-  return;
+    return a * b * c;
 }
 
 /* 
@@ -25,27 +24,27 @@ To run the tests for just this one file, type `npm test -- --testPathPattern 2-l
 */
 
 test("trimWord trims leading and trailing whitespace", () => {
-  expect(trimWord("   CodeYourFuture ")).toEqual("CodeYourFuture");
+    expect(trimWord("   CodeYourFuture ")).toEqual("CodeYourFuture");
 });
 
 test("trimWord doesn't remove whitespace in the middle of the string", () => {
-  expect(trimWord(" CodeYourFuture teaches coding     ")).toEqual(
-    "CodeYourFuture teaches coding"
-  );
+    expect(trimWord(" CodeYourFuture teaches coding     ")).toEqual(
+        "CodeYourFuture teaches coding"
+    );
 });
 
 test("getStringLength returns the length of a word", () => {
-  expect(getStringLength("Turtles")).toEqual(7);
+    expect(getStringLength("Turtles")).toEqual(7);
 });
 
 test("getStringLength returns the length of a sentence", () => {
-  expect(getStringLength("A wild sentence appeared!")).toEqual(25);
+    expect(getStringLength("A wild sentence appeared!")).toEqual(25);
 });
 
 test("multiply multiplies numbers", () => {
-  expect(multiply(2, 3, 6)).toEqual(36);
+    expect(multiply(2, 3, 6)).toEqual(36);
 });
 
 test("multiply multiplies different numbers", () => {
-  expect(multiply(2, 3, 4)).toEqual(24);
-});
+    expect(multiply(2, 3, 4)).toEqual(24);
+});
\ No newline at end of file
diff --git a/mandatory/3-function-output.js b/mandatory/3-function-output.js
index 5a953ba60..1f32f8ce9 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -1,16 +1,19 @@
 // Add comments to explain what this function does. You're meant to use Google!
 function getRandomNumber() {
-  return Math.random() * 10;
+    return Math.random() * 10; // random floating-point number from 0 to 10 
 }
 
 // Add comments to explain what this function does. You're meant to use Google!
 function combine2Words(word1, word2) {
-  return word1.concat(word2);
+    return word1.concat(word2); // return word1 + word2
 }
 
 function concatenate(firstWord, secondWord, thirdWord) {
-  // Write the body of this function to concatenate three words together.
-  // Look at the test case below to understand what this function is expected to return.
+    // Write the body of this function to concatenate three words together.
+    // Look at the test case below to understand what this function is expected to return.
+    return (firstWord + " ").concat((secondWord + " ").concat(thirdWord));
+    //another accepted approach
+    //return `${firstWord} ${secondWord} ${thirdWord}`;
 }
 
 /* 
@@ -25,13 +28,13 @@ To run the tests for just this one file, type `npm test -- --testPathPattern 3-f
 */
 
 test("concatenate example #1", () => {
-  expect(concatenate("code", "your", "future")).toEqual("code your future");
+    expect(concatenate("code", "your", "future")).toEqual("code your future");
 });
 
 test("concatenate example #2", () => {
-  expect(concatenate("I", "like", "pizza")).toEqual("I like pizza");
+    expect(concatenate("I", "like", "pizza")).toEqual("I like pizza");
 });
 
 test("concatenate doesn't only accept strings", () => {
-  expect(concatenate("I", "am", 13)).toEqual("I am 13");
-});
+    expect(concatenate("I", "am", 13)).toEqual("I am 13");
+});
\ No newline at end of file
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index ba77c7ae2..d32a99110 100644
--- a/mandatory/4-tax.js
+++ b/mandatory/4-tax.js
@@ -5,7 +5,9 @@
   Sales tax is 20% of the price of the product.
 */
 
-function calculateSalesTax() {}
+function calculateSalesTax(num) {
+    return num * 1.2;
+}
 
 /*
   CURRENCY FORMATTING
@@ -17,7 +19,9 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
+function addTaxAndFormatCurrency(num) {
+    return "£" + calculateSalesTax(num).toFixed(2);
+}
 
 /* 
 ===================================================
@@ -31,25 +35,25 @@ To run the tests for just this one file, type `npm test -- --testPathPattern 4-t
 */
 
 test("calculateSalesTax for £15", () => {
-  expect(calculateSalesTax(15)).toEqual(18);
+    expect(calculateSalesTax(15)).toEqual(18);
 });
 
 test("calculateSalesTax for £17.50", () => {
-  expect(calculateSalesTax(17.5)).toEqual(21);
+    expect(calculateSalesTax(17.5)).toEqual(21);
 });
 
 test("calculateSalesTax for £34", () => {
-  expect(calculateSalesTax(34)).toEqual(40.8);
+    expect(calculateSalesTax(34)).toEqual(40.8);
 });
 
 test("addTaxAndFormatCurrency for £15", () => {
-  expect(addTaxAndFormatCurrency(15)).toEqual("£18.00");
+    expect(addTaxAndFormatCurrency(15)).toEqual("£18.00");
 });
 
 test("addTaxAndFormatCurrency for £17.50", () => {
-  expect(addTaxAndFormatCurrency(17.5)).toEqual("£21.00");
+    expect(addTaxAndFormatCurrency(17.5)).toEqual("£21.00");
 });
 
 test("addTaxAndFormatCurrency for £34", () => {
-  expect(addTaxAndFormatCurrency(34)).toEqual("£40.80");
-});
+    expect(addTaxAndFormatCurrency(34)).toEqual("£40.80");
+});
\ No newline at end of file