Declare a class named MyNumbers.  It includes the following members:
1.  Data Member: num that is an integer array with size 20.
2.  Method: getSum which will find the sum of all numbers in data member.
3.  Method: getAvg which will find the average of all number in data member.
4.  Method: sort which sort the data in ascending order
5.  Method: print which print the data member.
6.  Constructor

In main function, you should read the data below from a data file and create an object to have the initial value as what you read:
     13  14  2  6  7  90  56  23  78  82  120  1  9  3  44  62  98  8  6  0
 

My suggestion to you is followed:

You create a project included three files: 

MyNumbers.h           declare class here
MyNumbers.cpp       implement methods and constructor here
Application.cpp         write main function here to create an object and call methods

Example:  The following three files are included in one project.

class Boy
{
  private:
     float Height, Weight;
  public:
    //Constructor 
    Boy(float Hei=0, float Wei=0);        
    void Grow(float H1);
    void Print(void);
}; 

#include"Boy.h"
#include<iostream>
using namespace std;

Boy::Boy(float Hei, float Wei)
{
	Height = Hei;
	Weight = Wei;
}

void Boy::Grow(float H1)
{
	Height = Height + H1;
}

void Boy::Print(void)
{
	cout<<"The height is "<<Height<<endl;
	cout<<"The weight is "<<Weight<<endl<<endl;
}

#include"Boy.h"
#include <iostream>
using namespace std;

void main()
{
	Boy Austin(70, 120);
	Austin.Print();
	Austin.Grow(12);
	Austin.Print();

	Boy Terry;
	Terry.Print();

	Boy Kenny(67);
	Kenny.Print();
}