C language: y = ((x=a+b),(b+c)) and y = (x=a+b),(b+c) Why are the results different

#include<stdio.h>

int main()
{
    
    
int a=2,b=4,c=6,x,y,q,p;
 y = ((x=a+b),(b+c));
 q = (p=a+b),(b+c);
printf ("%d,%d\n",x,y);
printf ("%d,%d\n",p,q);
return 0;
}

The precedence of the comma operator is lower than the equal sign,
so when you use the comma operator, you must add parentheses. For
example, this sentence

 q = (p=a+b),(b+c);

His meaning is
p = a+b;
q = p; the
latter, (b+c) is equivalent to void