What should I change to get discount

Question

#include<stdio.h>
void greeting ();
void discountcalculator(int x,int y,int s);
int main()
{
int x,y,s;
greeting ();
printf("Key in your age:");
scanf("%d",&x);
printf("Key in the amount you spent:");
scanf("%d",&y);
if(x>=18)
printf("Your age is %d and ",x);
else
("The age entered is invalid");

if(y>=1000)
printf("your discount is %d", s);
else
printf("You are not eligible for a discount.");
}
void greeting ()
{
printf("Welcome!\n");
}
void discountcalculator(int x,int y,int s)
{
printf("%d=%d*0.05",y*0.05);
scanf("%d",&s);
}

Answer 1

if(y>=1000)
printf("your discount is %lf", discountcalculator(y) ); // call function with y value passing.. No need of x, and s;

//and this is function which returns double type value discount to the call..
double discountcalculator(int y)
{
double s = y*0.05; // calculate
return s ; //change return type to double.
}