MATH!!!!!!!
posted by bert on .
The river boat paddled upstream at 12km/h, stopped for 2 h of sightseeing, and paddled back at 18km/h. How far upstream did the boat travel if the total time for the trip, including the stop, was 7h?
Please help me, the answer is 36 km but i have no idea how to set it up

Let D be the distance travelled. The total time moving was 7  2 = 5 hours.
Realize that time time spent travelling in one direction is D/V, where V is the speed.
Here is what you know:
D/12 + D/18 = 5 hours
Create a common denominator.
(3D + 2D)/36 = 5
5D/36 = 5
D = 36 km