The first thing we must do for this case is to define variables:
 x = rate of the rowing team in still water
 x + 5 = rate going with the current
 x-5 = rate going against the currrent
 Then, by definition we have:
 d = v * t
 Where
 d: distance
 v: speed
 t: time
 Clearing the time we have:
 t = d / v
 travel time is equal for downstream and upstream:
 60 / (x + 5) = 10 / (x-5)
 We clear x:
 60 (x-5) = 10 (x + 5)
 60x-300 = 10x + 50
 50x = 350
 x = 350/50
 x = 7
 Answer:
 The rate of the rowing team in still water is:
 x = 7 mph