A bag contains 12 balls out of which x are white.
(i) If one ball is drawn at random, what is the probability that it will be a white ball?
(ii) If 6 more white balls are put in the bag, the probability of drawing a white ball will be double than that in (I case). Find x.

A bag contains 12 balls out of which x are white.
(i) If one ball is drawn at random;
    P (Drawing a white ball ) =
(ii) 6 more white balls are put in the bag.
    Hence the number of balls in the bag = 12 + 6 = 18
    Number of white balls = x + 6
    P (Drawing a white ball )=
    P (Drawing a white ball in II case ) = 2 × P (Drawing a white ball in I case)      ⇒ = 2 ×          i.e x = 3