Final answer:
The boat's speed in still water, calculating from the upstream and downstream speeds given, is 21 mph. Note, this speed doesn't match any of the answer choices, suggesting a potential error in the question's data.
Step-by-step explanation:
To find the speed of the boat in still water, we first calculate the speed of the boat going upstream and downstream. When the boat travels upstream, it moves against the current, and when it travels downstream, it moves with the current.
The upstream speed is 60 miles in 2 hours which is 30 mph, and the downstream speed is 36 miles in 3 hours which is 12 mph. Let's denote the speed of the boat in still water as B and the speed of the current as C. The upstream speed is the boat's speed minus the current's speed (B - C), and the downstream speed is the boat's speed plus the current's speed (B + C).
Now we can set up two equations based on these calculations:
1. upstream: B - C = 30
2. downstream: B + C = 12
By adding these two equations, we eliminate C and can solve for B, which is the boat's speed in still water:
B - C + B + C = 30 + 12
2B = 42
B = 21 mph (which is not listed among the answer choices, hence there might be a mistake in the given data).