I'm having a bit of trouble understanding a probability distribution of 2 variables. Take for example taking n cards from a deck, and seeing what is the probability of getting X queens and say Y aces (with replacement). This involves the binomial distribution. The probabilities for the individual events are straight forward, but I'm having trouble getting the binomial coefficients. Normally, for one variable, the coefficient is just n C X ( n choose X) where n is the total number of trials. This is n! / X! (n-X)! ... but how do you get this now for an X and a Y???