Julie and Eric row their boat (at a constant speed) 27 miles downstream for 3 hours, helped by the current. Rowing at the same rate, the trip back against the current takes 9 hours. Find the rate of the current.

Let x, y be the speeds of boat, current.

3(x+y)=27.

9(x-y)=27.

x+y=9.

x-y=3 Byadding

2x=12

x=12/2 =6 mph.

y=9-x=9-6

=3 mph.

speed of boat =6 mph.

speed of current =3 mph.