Probability ? How do you find the intersection of the complements of two negatively dependent events? I'm given P(a), P(b), and P( A intersect B), but I need to find the conditional probability of 'the complement of B given the complement of A'. I don't know how to find it. I thought I only had to multiply the complements, but that obviously didn't work. Then I said maybe it's equal to the complement of the union of A and B: 1- ( A+B- A^B). Is that the right way of doing it? Thanks for your help.