If 55

_{x}+ 52_{x}= 77_{10}find X-
**A.**

5 -
**B.**

6 -
**C.**

7 -
**D.**

10

##### Correct Answer: Option C

##### Explanation

5*X^{1} + 5*X^{o} + 5*X^{1} + 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