-8 because when you add a negative number your basically subtracting its absolute value.
Answer: 60 miles
Step-by-step explanation:
Given
It takes ferry 2 hours to travel to town A and only
to travel back to town B.
Speed of current is 
Suppose the speed of the ferry is
mph
Distance traveled in both the cases is same, but it took more time traveling to city A that is, ferry is moving upstream and downstream for returning time.

Distance between the towns is 
The answer should be A simple interest