I think the answer is C.
There are two methods you can use for this kind of question.
First method:
Statement I. x is divisible by 12
36 is divisible by 12, 36 is also divisible by 36
48 is divisible by 12 but not divisible by 36.
Not Sufficient.
Statement II. x is divisible by 9
45 is divisible by 9, not by 36
72 is divisible by 9, also by 36
Not Sufficient.
Combining statement I & II
x is divisible by 12 as well as 9
36 is divisible by 36, 9 and 12
72 is divisible by 36, 9 and 12
108 is divisible by 36, 9 and 12
Second Method:
Find the prime factors of 36 = 2*2*3*3
Statement I.
Factors of 12 = 2*2*3 (notice we have one 3 missing) therefore some multiples of 12 will be multiples of 36 and some will not be.
Not Sufficient.
Statement II
Factors of 9 = 3*3 (we have two 2's missing)
Not Sufficient (same reasoning as above)
Combining Statement I & II
Factors of 9 and 12 together = 2*2*3*3*3 (notice we have one 3 extra)
Therefore every multiple of 12 and 9 together will also be a multiple of 36.
Hence C.
