word problem

Question

The speed of a stream is 2 mph. a boat travels 9 miles upstream in the same time it takes to travel 13 miles downstream. what is the speed of the boat in still water 

Answer 1

t=d/r

time = distance divided by rate of speed

t= 9/(r-2) = 13/(r+2)

9r+18 = 13r-26

4r = 44

r = 44/4 = 11 mph in still water

9/(11-2) = 13/(11+2) = 1 hour