Correct Answer - Option 2 : 8
Logic: First number x Third number = Square of middle number.
The pattern followed here is,
8 x 18 = 144 = (12)2
27 x 12 = 324 = (18)2
32 x ? = (16)2
32 x ? = 256
? = 256 / 32
? = 8
16 x 25 = 400 = (20)2
Hence, "8" is the correct answer.