Can anyone tell whats happening here

Question

#include <stdio.h>
int main()
{
static int x=25;
int f1() {x=x+1; return x;}
int f2() {x=x+2; return x;}
x=(f1(),f2());
printf("%d",x);
return 0;
}

Answer 1

output - 28
The comma is a binary operator in c language and act as sequence point.

Let me explain this in simpler terms the presence of comma operator guides the compiler to evaluate first operand and then discard the result got, after this it evaluates the second operand and returns the value as result.
In this case first F1() is evaluated that changed static x to 26 and afterwards F2() is evaluated which converted x= 26+2=28 and that stores in x.
Hope you understood.