Question

If a binary operation * is defined on the set Z of integers as a * b = 3a − b, then the value of (2 * 3) * 4 is
(a) 2
(b) 3
(c) 4
(d) 5

Answer 1

(d) 5

Given: a * b = 3a − b
2 * 3 = 3 (2) $-$ 3
= 6 $-$ 3
= 3

(2 * 3) * 4 = 3 * 4
= 3 (3) $-$ 4
= 9 $-$ 4
= 5