Question 6312
 Assume the rowing speed is Vr and the current speed is Vw.
 
 We have the downstream speed: Vr + Vw = 55/5 = 11 ...(1) 
 and the upstream speed    Vr - Vw = 55/11 = 5 ...(2)

 Hence, Vr = (11+5)/2 = 8 miles/hr and Vw = (11-5)/2 = 3 miles/hr


 Kenny
 PS: Usually, I don't answer such kind of simple question and similar
     questions appeared thousand times here.
     To avoid that you got terrible long solutions so I showed something
     that I learned when I was in elementary school and hope you don't 
     bother with this kinds of question any more.