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
[tex]\frac{1}{3} [/tex]
then how many white balls are in the box?
A) 15
B) 6
C) 9
D) 5
E) None of these

Pls give correct explanation of this answer. I will mark u as Brainliest​