Question 251802
There are several oddities in this word problem.
First, the first sentence confuses things. It states that Ben is paddling on  a different river. Different from what? Then the problem talks about streams. Is it a river or a stream? The same river as the stream or several different streams.
Furthermore, there is not enough info to calculate the rate of the current nor the length of the course.
There is a 4 hours difference in going upstream and going downstream. 
So the current makes a difference of two hours either by adding two hours or reducing it by two hours.
Without the current, it would probably take him 4 hours each direction all other things being equal.