A rowing team rowed 90

Question

A rowing team rowed 90

 miles while going with the current in the same amount of time as it took to row 10

 miles going against the current. The rate of the current was 4

 miles per hour. Find the rate of the rowing team in still water. 

what is the rate of the team still in water:

miles/hours

Answer 1

90/(4+r)=10/(r-4)

40+10r=90r-360

80r=400

r= 5 mph in still water