Answer E18

first  result: 5
second result: 1

#include <stdio.h>

/* Puzzle E18 -- precedence of arithmetic operators */
int main()
{
  int a = 5, b = 10 ;
  int result;
  
  result = a + a / b; 
  printf("first  result: %d\n", result ); 

  result = (a + a) / b;
  printf("second result: %d\n", result ); 
  
  return 0;
}

For the first result, the high-precidence / is done first, yielding an int 0. Then the value of a is added to that.

For the second result, the () force (a + a) to be done first, yielding an int 10. Then then that is divided by the value of b.