1. The problem statement, all variables and given/known data Let A and B be two events such that P(A) = 0.4, P(B) = 0.7, P(A∪B) = 0.9 Find P((A^c) - B) 2. Relevant equations I can't think of any relevant equations except maybe the Inclusion Exclusion property. P(A∪B) = P(A) + P(B) - P(A∩B) This leads us to another thing P(A∩B^c) = P(A-B) = P(A) - P(A∩B) And P(A^c) = 1 - P(A) 3. The attempt at a solution The primary problem I'm having is exchanging the equation for one I can easily understand. I know that P(A∩B) = 0.2 from the Inclusion Exclusion Property. However, I guess I'm having trouble comprehending the principles behind this math. I can't simply plug things in and expect it to work with the venn diagrams right? ex) I can't simply say A' = A^c = 1 - 0.4 = 0.6, and then have it in the form P(A'-B) = P(A') - P(A'∩B), Because then I have an equation with two unknowns... Using the In-Ex Prop, I'd have P(A'-B) = P(A') - P(A') + P(B) - P(A'∪B) Which basically leaves me in the same mess of too many variables. The logive behind Unions and Intersections really confuses me mathematically. I can visualize the venn diagrams for the most part, but translating that into a math and a function leaves me lost.