Here you go, a slightly fixed up version (with working decimals)

Code:

#include <stdio.h>
#include <stdlib.h>
int multi (int num1, int num2);
float divide (int num1, int num2);
int add (int num1, int num2);
int subtract (int num1, int num2);
int main()
{
int quit = 1, selection, num1, num2;
printf ("My Maths program, a work in progress\n\n\n");
while (quit != 2)
{
printf ("\nEnter the first number: \n");
scanf ("%d", &num1);
printf ("Enter the second number: \n");
scanf ("%d", &num2);
printf ("\n\n 1. Add them \n 2. Subtract the second number from the first \n 3. Multiply them \n 4. Divide the first number by the second \n\n What would you like to do with these numbers? ");
scanf ("%d\n", &selection);
switch (selection)
{
case 1:
printf("The answer is: %d\n\n", add (num1, num2));
break;
case 2:
printf("The answer is: %d\n\n", subtract (num1, num2));
break;
case 3:
printf("The answer is: %d\n\n", multi (num1, num2));
break;
case 4:
printf("The answer is: %f\n\n", divide (num1, num2));
break;
}
printf ("What would you like to do now? [1 = repeat, 2 = quit]\n");
scanf ("%d", &quit);
}
return 1;
}
int multi (int num1, int num2)
{
return num1*num2;
}
float divide (int num1, int num2)
{
return num1/num2;
}
int add (int num1, int num2)
{
return num1+num2;
}
int subtract (int num1, int num2)
{
return num1-num2;
}