How was increment equal to decrement here??

Question

In this code:
int main() {
int x=5,y=10,sum;
x-- ;
sum=x+y;
cout<<sum<<"\n";
cout<<x<<"\n";
//How come final result as 14 not 15?
return 0;
How come 14 not 15?

Answer 1

x-- is equivalent to x = x - 1; so after that statement x becomes 4.

Answer 2

You can just testing x value before displaying sum value with cout then you can understand why.
x--;
cout<<x<<endl;
sum = x+y;
cout<<sum<<"\n";

Answer 3

You decrement x and then you add x to sum, if you want sum to be 15, you have to do "sum = x + y" before "x--".