Before Brian starts messing with them, there are 24 balls in the bag.
9 of them are white.
-- The probability that Brian draws a white ball from the bag is (9/24) .
If he has already drawn one white ball and put it aside, then there are
23 balls left in the bag, and 8 of them are white.
-- The probability that Brian draws a white ball from the bag this time
is (8/23) .
So the probability of white balls on both draws is
(9/24) x (8/23) =
(72/552) =
3 / 23 = about 13% (rounded)