Answer:
0.3339 = 33.39% probability that both Dave and Mike will show up
Explanation:
Probability of independent events:
If A and B are independent events, the probability of both happening at the same time is given by:

In this question:
Event A: Dave shows up.
Event B: Mike shows up.
Christine knows that there is a 47% chance that Dave will not show up and a 37% chance that Mike will not show up.
This means that
.
a. What is the probability that both Dave and Mike will show up

0.3339 = 33.39% probability that both Dave and Mike will show up