On a Dart board, with different areas labeled as: A, B, C, D, and each area different sizes. The probabilities of each area are: P(A)=25%, P(B)=50%, P(C)=12.5% and P(D)=12.5%
What is P(~C or B)?
I don't understand the "not C or B" term. If it is not C then it includes B already. My guess would be 87.5%