A box contains 5 green marbles and 4 yellow marbles. Three marbles are drawn at random from the box without replacement. Find the probability that at least 2 yellow marbles are drawn given that at least one of each colour is drawn.

I've calculated the probability of drawing at least one of each colour is drawn. It's 5/6. The probability of drawing at least 2 yellow marbles is 17/42.

Now, how do I calculate the probability that at least 2 yellow marbles are drawn given that at least one of each colour is drawn? Many thanks in advance!