A bag contains 5 black, 4 white and x red marbles. If the probability of picking a red marble is

^{2}/_{3}, find the value of x-
**A.**

8 -
**B.**

10 -
**C.**

4 -
**D.**

6

##### Correct Answer: Option D

##### Explanation

Black = 5

White = 4

Red = x

Total = 9+x

P(red) = ^{2}/_{3}

x / (9+x) = ^{2}/_{5}

5x = 2(9+x)

5x = 18+2x

5x-2 = 18

3x = 18

x = 6