Answer: It will take Aaron's boat 3³/₅ hours to travel 18 miles upstream.
That is 3.6 hours or 3 hours and 36 minutes.
Step-by-step explanation:
Traveling upstream, the boat's speed will be reduced by the speed of the river current.
9 - 4 = 5mph
18mi/5mph = 3.6 hours 0r 3³/₅ hours
