question_answer

In a box, there are 7 red balls, x white balls   and 3 green balls. A ball is drawn from the box. If the probability of getting a white ball is found to be \[\frac{\mathbf{1}}{\mathbf{3}}\] then how many white balls in the box?

A)  15 

B)  6 

C)  9 

D)    5

E)  None of these