Aboat traveled 60 miles downstream and back. the trip downstream took 3 hours. the trip back took 30 hours. what is the sleep of the boat in still water ? what is the speed of the current ?

So we assume that the speed of the current was constant
Speed=distance/time
Distance=60
trip down=60/3=20mph
trip up=60/30=2mph
the speed of the current is the avavarage of the diffarence of 2 and 20 so the diffirance is 18  avagage is 9  so 9mph=speed of current  9+x=20 x=11 so the speed of the boat in still water is 11mph
the speed of the current is 9mph