When a softball player gets a hit, it can be a single, double, triple, or home run. when josephine is at bat, the probability that she hits a single is 15 percent and the probability that she hits a double is 5 percent what is the probability that josephine hits a single or a double when she is at bat?

Probability of hitting a single = P(S) = 0.15 (15%)
Probability of hitting a double = P(D) = 0.05 (5%)
These events are actually mutually exclusive, i.e. they cannot both occur in the same trial. In other words, she cannot hit a single and double in the same batting. This means:
P(S∩D) = Probability of hitting a single and double = 0 (0%) = impossible
Now, we use the formula:
P(S∪D) = P(S) + P(D) - P(S∩D)
P(S∪D) = Probability of hitting a single or double
So just sub in the values we have (It's simpler to do this with decimals I think, which is why I converted the percentages):
P(S∪D) = 0.15 + 0.05 - 0 = 0.2