college algebra
posted by Rosanna .
A boat can maintain a constant speed of 34 mph relative to the water. The boat makes a trip upstream to a certain point in 21 minutes; the return trip takes 13 minutes. What is the speed of the current?

Distance = rate * time
Let x = speed of current
rate upstream = 34  x
rate downstream = 34 + x
21(34  x) = 13(34 + x)
Solve for x.