When a crew rows with the current, it travels 18 miles in 3 hours. Against the current, the crew rows 6 miles in 3 hours. Let x=the crew's rowing rate in still water and let y = the rate of the current. Find the rate of rowing in still water and the rate of the current.

D=vt, distance equal velocity times time.

3 (x+y) = 18 and 3 (x-y) = 6 divide both equations by three

x+y=6 and x-y=2 now add the two equations together ...

x+x+y-y=6+2

2x=8 divide both sides by 2

x=4 mph, and since x+y=6

4+y=6

y=2 mph

So the speed of the boat in still water is 4mph and the speed of the current is 2mph.