One ball is drawn from a box containing 3 red, 2 blue and x green balls. Find the value of x so that the probability of drawing a green ball is double that of red or blue ball.
+37157 red or a blue = 5 out of (5+x)
green = x out of (5+x)
2 * 5/(5+x) = x / (5+x)
10 = x
