#define MULT_GOOD(x) ( (x) *  5 )
#define MULT_BAD(x) ( x *  5 )

int a = 2;
int b = 10;

int result1 = MULT_GOOD(a + b)
int result2 = MULT_BAD(a + b)

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int result1 = ((a + b) * 5)
int result2 = (a + b * 5)