90, 180, 12, 50, 100, 200, ?, 3, 50, 4, 25, 2, 6, 30, 3

Answer: Option A

Clearly, 90 = 30 x 3, 180 = 6 x 30, 12 = 2 x 6, 50 = 25 x 2, 100 = 4 x 25, 200 = 50 x 4.
So, missing term = 3 x 50 = 150.