IF 2=0, 3=3, 4=6, 5 = 9 then 7=?

Answer: (2) 15

Explanation:-
(2 + 0) = (0 x 3) = 2 = 0 ,
(2 + 1) = (1 x 3) = 3 = 3,
(3 + 1 ) = (2 x 3) = 4 = 6,
(4 + 1) = (3 x 3) = 5 = 9,
(5 + 1) = (4 x 3 ) = 6 = 12,

Same as,
(6 + 1) = (5 x 3) = 7 = 15.

Hence, the answer is (2) 15.