diff --git a/15_Day_Classes/15_day_starter/scripts/main.js b/15_Day_Classes/15_day_starter/scripts/main.js
index 4e66495..7a02c38 100644
--- a/15_Day_Classes/15_day_starter/scripts/main.js
+++ b/15_Day_Classes/15_day_starter/scripts/main.js
@@ -1,6 +1,6 @@
 
 
-class Person {
+/*class Person {
   constructor(firstName, lastName, age, country, city) {
     this.firstName = firstName
     this.lastName = lastName
@@ -102,4 +102,127 @@ console.log(s1.getPersonInfo())
 
 console.log(s2.saySomething())
 console.log(s2.getFullName())
-console.log(s2.getPersonInfo())
\ No newline at end of file
+console.log(s2.getPersonInfo())
+*/
+
+//Exercises Level 1
+
+//1.Create an Animal class. The class will have name, age, color, legs properties and create different methods
+class Animal {
+  constructor(name, age, color, legs){
+  this.name = name
+  this.age = age
+  this.color = color  
+  this.legs = legs
+  }
+  getInfo(){
+    return this.name + ' ' + ' ' + `age: ${this.age} color: ${this.color} legs: ${this.legs} ${this.gender}`
+  }
+
+}
+
+//2. Create a Dog and Cat child class from the Animal Class.
+let dog = new Animal('Firulais', 2, 'white', 4 )
+console.log(dog.getInfo())
+
+let cat = new Animal('Tom', 1, 'gray', 4)
+console.log(cat.getInfo())
+
+//Exercises Level 2
+
+//1. Override the method you create in Animal class
+class Reptile extends Animal {
+  constructor(name, age, color, legs, gender){
+    super(name, age, color, legs)
+    this.gender = gender
+  }
+  
+}
+
+let reptile = new Reptile('Lizard', 1, 'green', 4, 'male')
+console.log(reptile)
+//Exercises Level 3
+
+//1.Let's try to develop a program which calculate measure of central tendency of a sample(mean, median, mode) and measure of variability(range, variance, standard deviation). In addition to those measures find the min, max, count, percentile, and frequency distribution of the sample. You can create a class called Statistics and create all the functions which do statistical calculations as method for the Statistics class. Check the output below.
+ages = [31, 26, 34, 37, 27, 26, 32, 32, 26, 27, 27, 24, 32, 33, 27, 25, 26, 38, 37, 31, 34, 24, 33, 29, 26]
+class Statistics {
+
+  
+  mean = (arr) => {
+    const sum = arr.reduce((a, b) => a + b);
+    const count = arr.length;
+    // need to return explicitly
+    return ` Mean: ${Math.round(sum / count)}`  
+  }
+
+  median = (arr) => {
+    let median;
+    const sortedArr = arr.sort((a, b) => a - b);
+    if (arr.length % 2 != 0) {
+      median = sortedArr[(arr.length - 1) / 2];
+    } else {
+      median = (sortedArr[(arr.length / 2) - 1] + sortedArr[arr.length / 2]) / 2;
+    }
+    return  `Median: ${median}`;
+  }
+
+  mode = (arr) => {
+    const num = [...new Set(arr)];
+    const count = num.map((element) =>
+      arr.filter((number) => number === element).length)
+    let max = Math.max(...count);
+    let object = {};
+    object.mode = num[count.indexOf(max)];
+    object.count = max;
+    return object;
+  }
+}
+
+//count, sum, min, max, range
+
+
+let statistics = new Statistics()
+console.log(statistics.mean(ages), statistics.median(ages), statistics.mode(ages))
+//2.Create a class called PersonAccount. It has firstname, lastname, incomes, expenses properties and it has totalIncome, totalExpense, accountInfo,addIncome, addExpense and accountBalance methods. Incomes is a set of incomes and its description and expenses is also a set of expenses and its description.
+ages = [31, 26, 34, 37, 27, 26, 32, 32, 26, 27, 27, 24, 32, 33, 27, 25, 26, 38, 37, 31, 34, 24, 33, 29, 26]
+
+class PersonAccount {
+  constructor(firstName, lastName, incomes, expenses) {
+    this.firstName = firstName;
+    this.lastName  = lastName;
+    this.incomes = incomes;
+    this.expenses = expenses;
+  }
+  totalIncome() {
+    const incomeValues = Object.values(this.incomes);
+    const totalIncome = incomeValues.reduce((a, b) => a + b);
+    return totalIncome;
+  }
+  totalExpense() {
+    let expenseValues = Object.values(this.expenses);
+    const totalExpense = expenseValues.reduce((a, b) => a + b);
+    return totalExpense;
+  }
+  accountInfo() {
+    let incomeKeys = Object.keys(this.incomes);
+    let formattedIncomes = `${incomeKeys.slice(0, -1).join(', ')} and ${incomeKeys.slice(-1)}`;
+    let expenseKeys = Object.keys(this.expenses);
+    let formattedExpenses = `${expenseKeys.slice(0, -1).join(', ')} and ${expenseKeys.slice(-1)}`
+
+    let info = `This is ${this.firstName} ${this.lastName}'s account.\nThe user has incomes from ${formattedIncomes}.\nThe total income is ${this.totalIncome()}.\nThe user has expenses from ${formattedExpenses}.\nThe total expense is ${this.totalExpense()}.`
+    return info;
+  }
+  addIncome(source, value) {
+    this.incomes[`${source}`] = value;
+    return this.incomes;
+  }
+  addExpense(source, value) {
+    this.expenses[`${source}`] = value;
+    return this.expenses;
+  }
+}
+const account1 = new PersonAccount('Juan', 'Brink', {'salary' :  500, 'online course' : 700, 'part time' : 150}, {'bills' : 150, 'groceries' : 250});
+
+console.log(account1.accountInfo());
+console.log(account1.addIncome('flea market', 50));
+console.log(account1.addExpense('books', 30));
\ No newline at end of file