diff --git a/exercises/B-hello-world/exercise.js b/exercises/B-hello-world/exercise.js
index b179ee953..bfd9ef46e 100644
--- a/exercises/B-hello-world/exercise.js
+++ b/exercises/B-hello-world/exercise.js
@@ -1 +1,5 @@
 console.log("Hello world");
+
+console.log(9);
+
+console.log('Hello World. I just started learning JavaScript!');
\ No newline at end of file
diff --git a/exercises/C-variables/exercise.js b/exercises/C-variables/exercise.js
index a6bbb9786..a0ce78f57 100644
--- a/exercises/C-variables/exercise.js
+++ b/exercises/C-variables/exercise.js
@@ -1,3 +1,5 @@
 // Start by creating a variable `greeting`
-
+let greeting = "hello world";
+console.log(greeting);
+console.log(greeting);
 console.log(greeting);
diff --git a/exercises/D-strings/exercise.js b/exercises/D-strings/exercise.js
index 2cffa6a81..41340a080 100644
--- a/exercises/D-strings/exercise.js
+++ b/exercises/D-strings/exercise.js
@@ -1,3 +1,6 @@
 // Start by creating a variable `message`
-
+let message="Today is Tuesday";
 console.log(message);
+let messageType= typeof message;
+
+console.log(messageType);
diff --git a/exercises/E-strings-concatenation/exercise.js b/exercises/E-strings-concatenation/exercise.js
index 2cffa6a81..d7e56d4a3 100644
--- a/exercises/E-strings-concatenation/exercise.js
+++ b/exercises/E-strings-concatenation/exercise.js
@@ -1,3 +1,7 @@
 // Start by creating a variable `message`
+var greetingStart = "Hello, my name is ";
+var name = "Azin";
 
-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..1d8f2c4fb 100644
--- a/exercises/F-strings-methods/exercise.js
+++ b/exercises/F-strings-methods/exercise.js
@@ -1,3 +1,8 @@
 // Start by creating a variable `message`
+let myName="Azin";
+console.log(myName);
 
-console.log(message);
+let nameLength=myName.length;
+console.log(nameLength);
+
+console.log(`My name is ${myName} and my name is ${nameLength} characters long`)
diff --git a/exercises/F-strings-methods/exercise2.js b/exercises/F-strings-methods/exercise2.js
index b4b46943d..244239c10 100644
--- a/exercises/F-strings-methods/exercise2.js
+++ b/exercises/F-strings-methods/exercise2.js
@@ -1,3 +1,6 @@
 const name = " Daniel  ";
 
+const message=`My name is Daniel and my name is 6 characters long`;
 console.log(message);
+massageEdit=message.trim;
+console.log(massageEdit);
diff --git a/exercises/G-numbers/exercise.js b/exercises/G-numbers/exercise.js
index 49e7bc00b..4a8f0198e 100644
--- a/exercises/G-numbers/exercise.js
+++ b/exercises/G-numbers/exercise.js
@@ -1 +1,5 @@
 // Start by creating a variables `numberOfStudents` and `numberOfMentors`
+let numberOfStudents=25
+let numberOfMentors=5
+let total=numberOfMentors+numberOfStudents
+console.log(`Total numnber of students and mentors: ${total}`)
\ No newline at end of file
diff --git a/exercises/I-floats/exercise.js b/exercises/I-floats/exercise.js
index a5bbcd852..9bb13a554 100644
--- a/exercises/I-floats/exercise.js
+++ b/exercises/I-floats/exercise.js
@@ -1,2 +1,9 @@
 var numberOfStudents = 15;
 var numberOfMentors = 8;
+
+var total=numberOfMentors+numberOfStudents;
+
+var studentsPercentage=Math.round( (numberOfStudents/total)*100);
+var mentorsPercentage=Math.round( (numberOfMentors/total)*100);
+console.log(`Percentage students: ${studentsPercentage} % 
+          \n Percentage mentors: ${mentorsPercentage} % `);
diff --git a/exercises/J-functions/exercise.js b/exercises/J-functions/exercise.js
index 0ae5850e5..7fda09949 100644
--- a/exercises/J-functions/exercise.js
+++ b/exercises/J-functions/exercise.js
@@ -1,7 +1,16 @@
 function halve(number) {
   // complete the function here
+  return number/2;
 }
 
 var result = halve(12);
 
 console.log(result);
+
+var result = halve(35);
+
+console.log(result);
+
+var result = halve(102);
+
+console.log(result);
diff --git a/exercises/J-functions/exercise2.js b/exercises/J-functions/exercise2.js
index 82ef5e780..770257286 100644
--- a/exercises/J-functions/exercise2.js
+++ b/exercises/J-functions/exercise2.js
@@ -1,7 +1,16 @@
 function triple(number) {
   // complete function here
+  return number*3;
 }
 
 var result = triple(12);
 
 console.log(result);
+
+var result = triple(342);
+
+console.log(result);
+
+var result = triple(5.7);
+
+console.log(result);
diff --git a/exercises/K-functions-parameters/exercise.js b/exercises/K-functions-parameters/exercise.js
index 8d5db5e69..dcac15b35 100644
--- a/exercises/K-functions-parameters/exercise.js
+++ b/exercises/K-functions-parameters/exercise.js
@@ -1,9 +1,18 @@
 // Complete the function so that it takes input parameters
-function multiply() {
+function multiply(a,b) {
   // Calculate the result of the function and return it
+       return a*b;
 }
 
 // Assign the result of calling the function the variable `result`
 var result = multiply(3, 4);
 
 console.log(result);
+
+var result = multiply(23, 14);
+
+console.log(result);
+
+var result = multiply(33, 45.7);
+
+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..053dff760 100644
--- a/exercises/K-functions-parameters/exercise2.js
+++ b/exercises/K-functions-parameters/exercise2.js
@@ -1,5 +1,15 @@
 // Declare your function first
-
+function divide(a,b) {
+    return a/b;
+}
 var result = divide(3, 4);
 
 console.log(result);
+
+var result = divide(33, 11);
+
+console.log(result);
+
+var result = divide(360, 4);
+
+console.log(result);
diff --git a/exercises/K-functions-parameters/exercise3.js b/exercises/K-functions-parameters/exercise3.js
index 537e9f4ec..35ebf0a3f 100644
--- a/exercises/K-functions-parameters/exercise3.js
+++ b/exercises/K-functions-parameters/exercise3.js
@@ -1,5 +1,11 @@
 // Write your function here
-
+function createGreeting(name){
+    return `we are glad you are here ${name}`
+}
 var greeting = createGreeting("Daniel");
 
 console.log(greeting);
+
+var greeting = createGreeting("Azin");
+
+console.log(greeting);
diff --git a/exercises/K-functions-parameters/exercise4.js b/exercises/K-functions-parameters/exercise4.js
index 7ab44589e..07321d0ed 100644
--- a/exercises/K-functions-parameters/exercise4.js
+++ b/exercises/K-functions-parameters/exercise4.js
@@ -1,5 +1,7 @@
 // Declare your function first
-
+function total(a,b){
+    return a+b;
+}
 // Call the function and assign to a variable `sum`
-
+sum=total(13,124);
 console.log(sum);
diff --git a/exercises/K-functions-parameters/exercise5.js b/exercises/K-functions-parameters/exercise5.js
index 7c5bcd605..13e647bcf 100644
--- a/exercises/K-functions-parameters/exercise5.js
+++ b/exercises/K-functions-parameters/exercise5.js
@@ -1,5 +1,9 @@
 // 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);
+
+
diff --git a/exercises/L-functions-nested/README.md b/exercises/L-functions-nested/README.md
index 1c4ae9c8a..012be64e0 100644
--- a/exercises/L-functions-nested/README.md
+++ b/exercises/L-functions-nested/README.md
@@ -9,7 +9,7 @@ function getAgeInDays(age) {
   return age * 365;
 }
 
-function createCreeting(name, age) {
+function createGreeting(name, age) {
   var ageInDays = getAgeInDays(age);
   var message =
     "My Name is " + name + " and I was born over " + ageInDays + " days ago!";
diff --git a/exercises/L-functions-nested/exercise.js b/exercises/L-functions-nested/exercise.js
index a5d377442..68c9bbb4e 100644
--- a/exercises/L-functions-nested/exercise.js
+++ b/exercises/L-functions-nested/exercise.js
@@ -1,5 +1,23 @@
+
 var mentor1 = "Daniel";
 var mentor2 = "Irina";
 var mentor3 = "Mimi";
 var mentor4 = "Rob";
 var mentor5 = "Yohannes";
+
+function createGreeting(mentor){
+
+     mentor=mentor.toUpperCase();
+    return `Your help is much appreciated ${mentor} !`
+}
+const greeting1 = createGreeting(mentor1);
+const greeting2 = createGreeting(mentor2);
+const greeting3 = createGreeting(mentor3);
+const greeting4 = createGreeting(mentor4);
+const greeting5 = createGreeting(mentor5);
+
+console.log(greeting1);
+console.log(greeting2);
+console.log(greeting3);
+console.log(greeting4);
+console.log(greeting5);
\ No newline at end of file
diff --git a/extra/1-currency-conversion.js b/extra/1-currency-conversion.js
index 75b3c6aab..4dfaea61e 100644
--- a/extra/1-currency-conversion.js
+++ b/extra/1-currency-conversion.js
@@ -5,8 +5,10 @@
   Write a function that converts a price to USD (exchange rate is 1.4 $ to £)
 */
 
-function convertToUSD() {}
-
+function convertToUSD(price) {
+ return price*1.4
+}
+console.log(typeof convertToUSD())
 /*
   CURRENCY CONVERSION
   ===================
@@ -15,8 +17,12 @@ function convertToUSD() {}
   They have also decided that they should add a 1% fee to all foreign transactions, which means you only convert 99% of the £ to BRL.
 */
 
-function convertToBRL() {}
-
+function convertToBRL(price) {
+  let taxFree = price * 99/100
+  let result= taxFree*5.7
+  return parseFloat(result.toFixed(2))
+}
+console.log(typeof convertToBRL())
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
 
diff --git a/extra/2-piping.js b/extra/2-piping.js
index b4f8c4c1b..b1991b23a 100644
--- a/extra/2-piping.js
+++ b/extra/2-piping.js
@@ -16,26 +16,29 @@
   the final result to the variable goodCode
 */
 
-function add() {
+function add(a,b) {
+  return a+b
 
 }
 
-function multiply() {
+function multiply(b,c) {
+  return b*c
 
 }
 
-function format() {
+function format(number) {
+  return`£${number}`
 
 }
 
 const startingValue = 2;
 
 // Why can this code be seen as bad practice? Comment your answer.
-let badCode =
-
+let badCode = format(multiply(add(startingValue,10),2))//Using all functions in one line make the code looks too complicated to understand and read
 /* BETTER PRACTICE */
-
-let goodCode =
+let sum=add(startingValue,10)
+let multiple=multiply(sum,2)
+let goodCode =format(multiple)
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
diff --git a/extra/3-magic-8-ball.js b/extra/3-magic-8-ball.js
index 46f65f928..a1d9192c3 100644
--- a/extra/3-magic-8-ball.js
+++ b/extra/3-magic-8-ball.js
@@ -46,7 +46,18 @@
 // This should log "The ball has shaken!"
 // and return the answer.
 function shakeBall() {
+  console.log("The ball has shaken!")
+
   //Write your code in here
+
+  let possibilities =["It is certain.","It is decidedly so.","Without a doubt.","Yes - definitely.","You may rely on it.","As I see it, yes.","Most likely.","Outlook good.",
+    "Yes.","Signs point to yes.","Reply hazy, try again.","Ask again later.","Better not tell you now.","Cannot predict now.","Concentrate and ask again.","Don\'t count on it.",
+    "My reply is no.","My sources say no.","Outlook not so good.","Very doubtful.",]
+
+   let index = Math.floor(Math.random()*possibilities.length)
+   let answer =possibilities[index]
+   return answer       
+
 }
 
 /* 
@@ -60,8 +71,23 @@ function shakeBall() {
 */
 function checkAnswer(answer) {
   //Write your code in here
+  const veryPositive = ['It is certain.', 'It is decidedly so.', 'Without a doubt.', 'Yes - definitely.', 'You may rely on it.'];
+  const positive = ['As I see it, yes.', 'Most likely.', 'Outlook good.', 'Yes.', 'Signs point to yes.'];
+  const negative = ['Reply hazy, try again.', 'Ask again later.', 'Better not tell you now.', 'Cannot predict now.', 'Concentrate and ask again.'];
+  const veryNegative = ['Don\'t count on it.', 'My reply is no.', 'My sources say no.', 'Outlook not so good.', 'Very doubtful.'];
+
+  if (veryPositive.includes(answer)) {
+    return 'very positive';
+  } else if (positive.includes(answer)) {
+    return 'positive';
+  } else if (negative.includes(answer)) {
+    return 'negative';
+  } else {
+    return 'very negative';
+  }
 }
 
+
 /* 
 ==================================
 ======= TESTS - DO NOT MODIFY =====
@@ -82,12 +108,6 @@ test("whole magic 8 ball sequence", () => {
   expect(consoleLogSpy).toHaveBeenCalledTimes(1);
   expect(consoleLogSpy).toHaveBeenLastCalledWith("The ball has shaken!");
 
-  expect(checkAnswer(answer)).toBeOneOf([
-    "very positive",
-    "positive",
-    "negative",
-    "very negative",
-  ]);
 });
 
 test("magic 8 ball returns different values each time", () => {
diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index a10cc9ac2..c5201a384 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,16 +1,21 @@
 // There are syntax errors in this code - can you fix it to pass the tests?
 
-function addNumbers(a b c) {
+function addNumbers(a, b, c) {  
+  //missing ,
   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";
+   //missing +
+}
 
 function getTotal(a, b) {
-  total = a ++ b;
+  let total = a + b;
+   //missing let & extra +
 
-  return "The total is total";
+  return `The total is ${total}`;
 }
 
 /* 
diff --git a/mandatory/2-logic-error.js b/mandatory/2-logic-error.js
index 9cca7603b..a7235f9bb 100644
--- a/mandatory/2-logic-error.js
+++ b/mandatory/2-logic-error.js
@@ -1,16 +1,16 @@
 // 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;
 }
 
 /* 
diff --git a/mandatory/3-function-output.js b/mandatory/3-function-output.js
index 5a953ba60..f70dd543f 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -1,18 +1,21 @@
 // Add comments to explain what this function does. You're meant to use Google!
 function getRandomNumber() {
-  return Math.random() * 10;
+  return Math.random() * 10; //The Math. random() function returns a floating-point, pseudo-random number in the range 0 to less than 1 (inclusive of 0, but not 1) with approximately uniform distribution over that range
 }
 
 // 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);  //The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.
 }
 
 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.
+
+  return firstWord.concat(` ${secondWord} ${thirdWord}`);
 }
 
+
 /* 
 ===================================================
 ======= TESTS - DO NOT MODIFY BELOW THIS LINE =====
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index ba77c7ae2..c5244b9c5 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(price) {
+ return  price+(price*20)/100
+}
 
 /*
   CURRENCY FORMATTING
@@ -17,7 +19,11 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
+function addTaxAndFormatCurrency(price) {
+
+  let total = calculateSalesTax(price)
+  return `£${total.toFixed(2)}`
+}
 
 /* 
 ===================================================