rate and total distance problem?

Question

Abe can row a boat at constant rate of 5 miles per hr in still water. on a river that flows with a constant current of x miles per hr, he rows up stream for 15mins and then rows down stream, returning to his starting point in another 12 mins. find the current's rate and total distance noah traveled on his boat trip

Answer 1

So his up stream rate is (5 - x) miles per hr and his down stream rate is (5 + x) miles per hr. Obviously, he covered the same distance by rowing 15min (or 1/4 hr) up stream or by rowing 12min (or 1/5 hr) down stream. Therefore:
(5 - x)/4 = (5 + x)/5
25 - 5x = 20 + 4x
x = 5/9
and (5 - x)/4 = (5 + x)/5 = 10/9
That is to say, the current's rate is 5/9 miles per hr, and he traveled on his boat upsteam or down-stream for 10/9 miles, thus his total boat trip is 20/9 miles.