Why my code no run.It's bug in void nhap and no run

Question

#include <stdio.h>
void nhap( int &a, int &b);
int tinhTong(int a, int b);
void xuat(int c);
int main() {
int a, b;
nhap(a,b);
int c= tinhTong(a,b);
xuat(c);
}
void nhap( int &a, int &b){
scanf("%d %d",&a, &b);
}
int tinhTong(int a, int b){
int c= a+b;
return c;
}
void xuat(int c){
printf("%d",c);
}

Answer 1

Error in prototype of nhap, and call'it inside main