It takes a motorboat 6 hours to travel 96 miles down a river, and 2 hours longer to make the return trip. find the speed of the current.

Speed = distance / time
Down river> 96/6 = 16 mph
up river< 96/(6+2) = 12 mph
difference of 4 mph or +- 2 mph
14 + 2 for down river or with the flow
14 - 2 for up river, against the flow
so the speed of the river is 2 mph
((16+12)/2)-12 = 2 or ((16+12)/2)-16 = -2 depending on which way you define to be positive -- Speed is scaler anyway so can only be positive
the speed of the boat in still water is 14 mph