follow the operator precedence rules . you will get ans 10. Product(x+4,y-3) expands to x + 4 * y - 3 => 5 + (4 * 2) - 3 => (5 + 8) - 3 =10.
Instead of macro if you had used normal function like this
int product(int a, int b)
{
return a*b;
}
then the answer will be -9