Question 351528
still water speed = xmph
current speed = y mph
...
Time = distance / speed
upstream time = 6/ (x-y ) =(3/4)
3(x-y ) =6*4
x-y = 8.................1
downstream speed = 6/(x+y) = (1/2) 
x+y = 12.................2
add 1 & 2
2x=20
x=10 mph speed of boat.
x-y =8 
so y =2 mph speed of current