The idea is just try to make a square number inside the sqrt.
49 no good cuz 63-49 not divisible by 3, and the way to check for the rest that doesn't work or works is to see whether it's divisible by 3 or not.
36 works for x = 81
25 no good
16 no good
9 works for x = 324
4 no good
1 no good.
Real Values can only be x = 81 or x = 324, so answer is 2.