Two Approaches to Calculating Combined Percentages

Question

Upon some event there is a 50% chance that something has a 75% chance of happening. It is my understanding that there is a $.75/2 = .375$ probability of this. Is there any way to know the probability if the first event does not occur?

Answer 1

We do not know what the chance is if the $50$% are not hit. Therefore, we cannot determine the actual chance.

Answer 2

Dispute it effectively by pointing out that $$ \frac{2}{8} + \frac{1}{8} = .375 \neq .325 $$