On a float trip, Kim traveled 48 miles downstream in the same amount of time that it would take her to row 30miles upstream. If her speed in still water is 13 mph, find the speed of the current.
rate * time = distance
(13-c) t = 30 13t - ct =30
(13+c) t = 48 13t + ct = 48 add these two equations together : 26t = 78 t = 3
now subtitute this value of 't' into one of the equations to solve for 'c'