The correct formula for interpreting the probability of either event A or event B occurring (the probability of the union of A and B) is:
\[ P(A) + P(B) - P(A \text{ and } B) \]
This accounts for the fact that if both events A and B can occur together, the probability of their intersection \(P(A \text{ and } B)\) needs to be subtracted to avoid double counting.
So the answer is:
P(A) + P(B) − P(A and B)