If 55x + 52x = 7710 find X

If 55_x + 52_x = 77₁₀ find X

Correct Answer: Option C

Explanation

5*X¹ + 5*X^o + 5*X¹ + 2*X^o = 77 (change to base 10)
5*X + 5*1 + 5*X + 2*1 = 77
5X + 5 + 5X + 2 = 77
10X + 7 = 77
10X = 77-7
10X = 70
X = 70/10
X = 7