View Compilation Error

0_0_39371325_23944.cpp: In function 'int main()':
0_0_39371325_23944.cpp:10:17: error: 'a' was not declared in this scope
   10 |                 a=(x+y)/2;
      |                 ^
0_0_39371325_23944.cpp:11:17: error: 'b' was not declared in this scope
   11 |                 b=x-a;
      |                 ^