a box contains 2 red and 3 blue marbles. Find the probaility that if 2 marbles are drawn at random 1 is red and 1 is blue (without replacement)

P(1\ red,\ 1\ blue | 2\ drawn) = \frac{P(1\ red,\ 1\ blue\ \cap\ 2\ drawn)}{P(2\ drawn)}

What is the probability of picking any two balls?
What is the probability of picking a red and a blue ball?

Find those, use this in the formula and you'll be done. Post what you get! :)