a.  Write C++ statements that include the header files iostream.
b.  Write a C++ statement that allows you to use cin, cout, and endl
    without the prefix std::.
c.  Write C++ statements that declare the following variables: num1, num2,
    num3, and average of type int.
d.  Write C++ statements that store 125 into num1, 28 into num2, and
    -25 into num3.
e.  Write a C++ statement that stores the average of num1, num2, and
    num3, into average.
f.  Write C++ statements that output the values of num1, num2, num3,
    and average.
g.  Compile and run your program.

Code:

#include <iostream>

using namespace std;

int main()
{
  int num1, num2, num3;
  
  num1 = 125;
  num2 = 28;
  num3 = -25;
  int average = 0;

  average = (num1 + num2 + num3) / 3;

  cout << "Num 1 = " << num1 << endl;
  cout << "Num 2 = " << num2 << endl;
  cout << "Num 3 = " << num3 << endl;
  cout << "Average = " << average << endl;
  
  return 0;
}