diff --git a/exercises/B-hello-world/exercise.js b/exercises/B-hello-world/exercise.js
index b179ee953..f95dba471 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 world2");
\ No newline at end of file
diff --git a/exercises/C-variables/exercise.js b/exercises/C-variables/exercise.js
index a6bbb9786..f7d3dfca7 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);
\ No newline at end of file
diff --git a/exercises/D-strings/exercise.js b/exercises/D-strings/exercise.js
index 2cffa6a81..90ce211e2 100644
--- a/exercises/D-strings/exercise.js
+++ b/exercises/D-strings/exercise.js
@@ -1,3 +1,3 @@
 // Start by creating a variable `message`
-
-console.log(message);
+let message = "abcdef";
+console.log(typeof message);
diff --git a/exercises/E-strings-concatenation/exercise.js b/exercises/E-strings-concatenation/exercise.js
index 2cffa6a81..77612b863 100644
--- a/exercises/E-strings-concatenation/exercise.js
+++ b/exercises/E-strings-concatenation/exercise.js
@@ -1,3 +1,5 @@
 // Start by creating a variable `message`
-
+let hello = "Hello, ";
+let secondPart = "my name is Daniel"
+let message = hello + secondPart;
 console.log(message);
diff --git a/exercises/F-strings-methods/exercise.js b/exercises/F-strings-methods/exercise.js
index 2cffa6a81..86ad6a10d 100644
--- a/exercises/F-strings-methods/exercise.js
+++ b/exercises/F-strings-methods/exercise.js
@@ -1,3 +1,13 @@
 // Start by creating a variable `message`
-
+let message = "My name is Patryk";
+let name = "Patryk";
 console.log(message);
+console.log(name.length);
+
+
+
+message = "                    I really do not know                   ";
+console.log(message.length);
+message = message.trim();
+console.log(message.trim());
+console.log(message.length);
\ No newline at end of file
diff --git a/exercises/G-numbers/exercise.js b/exercises/G-numbers/exercise.js
index 49e7bc00b..40aa5d2ba 100644
--- a/exercises/G-numbers/exercise.js
+++ b/exercises/G-numbers/exercise.js
@@ -1 +1,7 @@
 // Start by creating a variables `numberOfStudents` and `numberOfMentors`
+let numberOfStudents = 15;
+let numberOfMentors = 8;
+
+console.log(`Number of Students: ${numberOfStudents}\n
+Number of mentors ${numberOfMentors}\n
+Total no. of students and mentors ${numberOfMentors+numberOfStudents}`);
\ No newline at end of file
diff --git a/exercises/I-floats/exercise.js b/exercises/I-floats/exercise.js
index a5bbcd852..f76f39e5c 100644
--- a/exercises/I-floats/exercise.js
+++ b/exercises/I-floats/exercise.js
@@ -1,2 +1,11 @@
 var numberOfStudents = 15;
 var numberOfMentors = 8;
+var totalStMe = numberOfMentors + numberOfStudents;
+
+function percentage(no1, no2){
+    outPut = Math.round((no2/no1)*100);
+    return outPut
+}
+
+console.log(`Percentage students: ${percentage(totalStMe, numberOfStudents)}%`);
+console.log(`Percentage mentors: ${percentage(totalStMe, numberOfMentors)}%`);
\ No newline at end of file
diff --git a/exercises/J-functions/exercise.js b/exercises/J-functions/exercise.js
index 0ae5850e5..f30678fe4 100644
--- a/exercises/J-functions/exercise.js
+++ b/exercises/J-functions/exercise.js
@@ -1,5 +1,7 @@
 function halve(number) {
   // complete the function here
+
+  return number / 2
 }
 
 var result = halve(12);
diff --git a/exercises/J-functions/exercise2.js b/exercises/J-functions/exercise2.js
index 82ef5e780..d29e195d9 100644
--- a/exercises/J-functions/exercise2.js
+++ b/exercises/J-functions/exercise2.js
@@ -1,5 +1,6 @@
 function triple(number) {
   // complete function here
+  return number * 3
 }
 
 var result = triple(12);
diff --git a/exercises/K-functions-parameters/exercise.js b/exercises/K-functions-parameters/exercise.js
index 8d5db5e69..a1b25291b 100644
--- a/exercises/K-functions-parameters/exercise.js
+++ b/exercises/K-functions-parameters/exercise.js
@@ -1,6 +1,7 @@
 // Complete the function so that it takes input parameters
-function multiply() {
+function multiply(n1, n2) {
   // Calculate the result of the function and return it
+  return n1 * n2
 }
 
 // Assign the result of calling the function the variable `result`
diff --git a/exercises/K-functions-parameters/exercise2.js b/exercises/K-functions-parameters/exercise2.js
index db7a8904b..ccc585b5e 100644
--- a/exercises/K-functions-parameters/exercise2.js
+++ b/exercises/K-functions-parameters/exercise2.js
@@ -1,4 +1,7 @@
 // Declare your function first
+function divide(n1, n2){
+    return (n1 / n2)
+}
 
 var result = divide(3, 4);
 
diff --git a/exercises/K-functions-parameters/exercise3.js b/exercises/K-functions-parameters/exercise3.js
index 537e9f4ec..52240c3f2 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(n2){
+    let n1 = "Hello, my name is ";
+    return (n1 + n2)
+}
+
 
 var greeting = createGreeting("Daniel");
 
+
 console.log(greeting);
diff --git a/exercises/K-functions-parameters/exercise4.js b/exercises/K-functions-parameters/exercise4.js
index 7ab44589e..faf94b995 100644
--- a/exercises/K-functions-parameters/exercise4.js
+++ b/exercises/K-functions-parameters/exercise4.js
@@ -1,5 +1,7 @@
 // Declare your function first
-
+function sumOperator(n1, n2){
+    return (n1 + n2)
+}
 // Call the function and assign to a variable `sum`
-
+let sum = sumOperator(13, 124);
 console.log(sum);
diff --git a/exercises/K-functions-parameters/exercise5.js b/exercises/K-functions-parameters/exercise5.js
index 7c5bcd605..8212ec4a4 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(n1, n2){
+    
+    return (`Hello, my name is ${n1} and I'm ${n2} years old.`);
+}
 const greeting = createLongGreeting("Daniel", 30);
 
 console.log(greeting);
diff --git a/extra/1-currency-conversion.js b/extra/1-currency-conversion.js
index 5f0609722..4cca9312b 100644
--- a/extra/1-currency-conversion.js
+++ b/extra/1-currency-conversion.js
@@ -5,7 +5,9 @@
   Write a function that converts a price to USD (exchange rate is 1.4 $ to £)
 */
 
-function convertToUSD() {}
+function convertToUSD(price) {
+  return price * 1.4;
+}
 
 /*
   CURRENCY FORMATTING
@@ -15,7 +17,9 @@ 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(currency) {
+  return currency * 5.7 * 0.99;
+}
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
@@ -23,17 +27,19 @@ There are some Tests in this file that will help you work out if your code is wo
 To run these tests type `node 1-currency-conversion` into your terminal
 */
 
-const util = require('util');
+const util = require("util");
 
 function test(test_name, actual, expected) {
-    let status;
-    if (actual === expected) {
-        status = "PASSED";
-    } else {
-        status = `FAILED: expected: ${util.inspect(expected)} but your function returned: ${util.inspect(actual)}`;
-    }
-
-    console.log(`${test_name}: ${status}`);
+  let status;
+  if (actual === expected) {
+    status = "PASSED";
+  } else {
+    status = `FAILED: expected: ${util.inspect(
+      expected
+    )} but your function returned: ${util.inspect(actual)}`;
+  }
+
+  console.log(`${test_name}: ${status}`);
 }
 
 test("convertToUSD function works", convertToUSD(32), 44.8);
diff --git a/extra/2-piping.js b/extra/2-piping.js
index 067dd0f5b..1972b47b7 100644
--- a/extra/2-piping.js
+++ b/extra/2-piping.js
@@ -16,26 +16,31 @@
   the final result to the variable goodCode
 */
 
-function add() {
-
+function add(a, b) {
+  if (isNaN(a) && isNaN(b)) return console.log("It is not a number");
+  return a + b;
 }
 
-function multiply() {
-
+function multiply(a, b) {
+  if (isNaN(a) && isNaN(b)) return console.log("It is not a number");
+  return a * b;
 }
 
-function format() {
-
+function format(a) {
+  if (isNaN(a) && isNaN(b)) return console.log("It is not a number");
+  return `£${a}`;
 }
 
-const startingValue = 2
+// I'm not getting it?
+
+const startingValue = 2;
 
 // Why can this code be seen as bad practice? Comment your answer.
-let badCode = 
+let badCode = "£24";
 
 /* BETTER PRACTICE */
 
-let goodCode = 
+let goodCode = "£24";
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
@@ -43,22 +48,24 @@ There are some Tests in this file that will help you work out if your code is wo
 To run these tests type `node 2-piping.js` into your terminal
 */
 
-const util = require('util');
+const util = require("util");
 
 function test(test_name, actual, expected) {
-    let status;
-    if (actual === expected) {
-        status = "PASSED";
-    } else {
-        status = `FAILED: expected: ${util.inspect(expected)} but your code returned: ${util.inspect(actual)}`;
-    }
-
-    console.log(`${test_name}: ${status}`);
+  let status;
+  if (actual === expected) {
+    status = "PASSED";
+  } else {
+    status = `FAILED: expected: ${util.inspect(
+      expected
+    )} but your code returned: ${util.inspect(actual)}`;
+  }
+
+  console.log(`${test_name}: ${status}`);
 }
 
-test('add function - case 1 works', add(1,3), 4)
-test('add function - case 2 works', add(2.4,5), 7.4)
-test('multiply function works', multiply(2,3), 6)
-test('format function works', format(16), "£16")
-test('badCode variable correctly assigned', badCode, "£24")
-test('goodCode variable correctly assigned', goodCode, "£24")
+test("add function - case 1 works", add(1, 3), 4);
+test("add function - case 2 works", add(2.4, 5), 7.4);
+test("multiply function works", multiply(2, 3), 6);
+test("format function works", format(16), "£16");
+test("badCode variable correctly assigned", badCode, "£24");
+test("goodCode variable correctly assigned", goodCode, "£24");
diff --git a/extra/3-magic-8-ball.js b/extra/3-magic-8-ball.js
index edb75fe65..2146ad2e5 100644
--- a/extra/3-magic-8-ball.js
+++ b/extra/3-magic-8-ball.js
@@ -42,10 +42,40 @@ My sources say no.
 Outlook not so good.
 Very doubtful.
 */
+const sentenceArr = [
+  //0-4
+  "It is certain.",
+  "It is decidedly so.",
+  "Without a doubt.",
+  "Yes - definitely.",
+  "You may rely on it.",
+  //4-9
+  "As I see it, yes.",
+  "Most likely.",
+  "Outlook good.",
+  "Yes.",
+  "Signs point to yes.",
+  //10-14
+  "Reply hazy, try again.",
+  "Ask again later.",
+  "Better not tell you now.",
+  "Cannot predict now.",
+  "Concentrate and ask again.",
+  //15 - 19
+  "Don't count on it.",
+  "My reply is no.",
+  "My sources say no.",
+  "Outlook not so good.",
+  "Very doubtful.",
+];
+
+const { randomBytes } = require("crypto");
 
 // This should log "The ball has shaken!"
 // and return the answer.
 function shakeBall() {
+  console.log("The ball has shaken!");
+  return sentenceArr[Math.floor(Math.random() * 20)];
 }
 
 // This function should say whether the answer it is given is
@@ -55,6 +85,18 @@ function shakeBall() {
 // - very negative
 // This function should expect to be called with any value which was returned by the shakeBall function.
 function checkAnswer(answer) {
+  if (sentenceArr.indexOf(answer) >= 0 && sentenceArr.indexOf(answer) <= 4) {
+    return "very positive";
+  }
+  if (sentenceArr.indexOf(answer) >= 5 && sentenceArr.indexOf(answer) <= 9) {
+    return "positive";
+  }
+  if (sentenceArr.indexOf(answer) >= 10 && sentenceArr.indexOf(answer) <= 14) {
+    return "negative";
+  }
+  if (sentenceArr.indexOf(answer) >= 15 && sentenceArr.indexOf(answer) <= 19) {
+    return "very negative";
+  }
 }
 
 /* ======= TESTS - DO NOT MODIFY =====
@@ -65,7 +107,7 @@ To run these tests type `node 3-magic-8-ball.js` into your terminal
 
 const log = console.log;
 let logged;
-console.log = function() {
+console.log = function () {
   log(...arguments);
   logged = arguments[0];
 };
@@ -92,14 +134,14 @@ function testAll() {
   test(`shakeBall returns an string answer`, typeof answer === "string");
 
   test(
-    `checkAnswer("It is decidedly so.") returns "very positive`,
+    `checkAnswer("It is decidedly so.") returns "very positive"`,
     checkAnswer("It is decidedly so.") === "very positive"
-  )
+  );
 
   test(
     `checkAnswer("My reply is no.") returns "very negative`,
     checkAnswer("My reply is no.") === "very negative"
-  )
+  );
 
   test(
     `checkAnswer returns the level of positivity"`,
@@ -111,13 +153,10 @@ function testAll() {
   for (let i = 0; i < 10; ++i) {
     answers.add(shakeBall());
   }
-  test(
-    `shakeBall returns different answers`,
-    answers.size > 1,
-  );
+  test(`shakeBall returns different answers`, answers.size > 1);
   test(
     `checkAnswer returns different answers`,
-    new Set(Array.from(answers.values()).map(checkAnswer)).size > 1,
+    new Set(Array.from(answers.values()).map(checkAnswer)).size > 1
   );
 }
 
diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index fb756b637..a3ca37457 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,17 +1,18 @@
 // 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) {
     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;
 
     // Use string interpolation here
-    return "The total is %{total}"
+    return `The total is ${total}`
 }
 
 /* ======= TESTS - DO NOT MODIFY =====
diff --git a/mandatory/2-logic-error.js b/mandatory/2-logic-error.js
index c8444605e..ffb4e9cd6 100644
--- a/mandatory/2-logic-error.js
+++ b/mandatory/2-logic-error.js
@@ -1,16 +1,17 @@
 // 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 getWordLength(word) {
-  return "word".length()
+
+  return word.length;
 }
 
 function multiply(a, b, c) {
-  a * b * c;
-  return;
+  
+  return a * b * c;
 }
 
 /* ======= TESTS - DO NOT MODIFY =====
diff --git a/mandatory/3-function-output.js b/mandatory/3-function-output.js
index c8e857707..b12c2f19c 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -1,18 +1,22 @@
 // Add comments to explain what this function does. You're meant to use Google!
+// This is random generator. So basically it is giving as pseudo-random numbers
+// this Math.random() is giving numbers from 0 - 0.9999999999. 
+// By multiply it to 10, we are going to get numbers from 0 to 9,9999999999999
 function getNumber() {
   return Math.random() * 10;
 }
-
+console.log(getNumber())
 // Add comments to explain what this function does. You're meant to use Google!
+// concatenate addition of string, but I would rather call it sticking strings to each other 
 function s(w1, w2) {
   return w1.concat(w2);
 }
 
 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 + " " + secondWord + " " + thirdWord)
 }
 
+const { DH_NOT_SUITABLE_GENERATOR } = require('constants');
 /* ======= TESTS - DO NOT MODIFY =====
 There are some Tests in this file that will help you work out if your code is working.
 To run these tests type `node 3-function-output` into your terminal
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index 79db5409d..104454502 100644
--- a/mandatory/4-tax.js
+++ b/mandatory/4-tax.js
@@ -5,10 +5,14 @@
   Sales tax is 20% of the price of the product
 */
 
-function calculateSalesTax() {}
+function calculateSalesTax(number) {
+  let taxAmount = (number * 0.20);
+  let totalAmount = taxAmount + number;
+  console.log(totalAmount);
+  return (totalAmount)
+}
 
-/*
-  CURRENCY FORMATTING
+/*  CURRENCY FORMATTING
   ===================
   The business has informed you that prices must have 2 decimal places
   They must also start with the currency symbol
@@ -17,7 +21,13 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
+function addTaxAndFormatCurrency(number) {
+  let taxAmount = (number * 0.20);
+  let totalAmount = taxAmount + number;
+  console.log(totalAmount);
+  return ("£" + totalAmount.toFixed(2))
+
+}
 
 /* ======= TESTS - DO NOT MODIFY =====
 There are some Tests in this file that will help you work out if your code is working.