The previous example doubled a sum. This time the request calls for three groups of 2 + 3 parts. Parentheses must keep the sum together before multiplication; the argument has no side effects.
TRIPLE(x) with parentheses around both the parameter and the whole result, multiplying by 3. Keep the supplied call TRIPLE(2 + 3) so the program prints Parts: 15 with a newline.Use #define TRIPLE(x) ((x) * 3).