Answer:
A 1 1/2 miles per hour
Step-by-step explanation:
Take the amount of miles he can row in 1/4 of an hour (3/8) and multiply it by 4, since it will tell you how many miles he can row in one hour. You get 12/8 miles per hour, which simplifies to 1 1/2 miles per hour
Hopefully this helps - let me know if you have any questions!