24.
( 6*3+ 2*3). logical since 3*3=9, 4*3=12+2x here x=1, and finally 6*3=18 + 3x, here x=2 since it increments from the beginning.
( 6*3+ 2*3). logical since 3*3=9, 4*3=12+2x here x=1, and finally 6*3=18 + 3x, here x=2 since it increments from the beginning.