Question 522559
downstream, a boat can go 12 miles in 2 hours. 

Going upstream, 12* 2/3 =>8 miles in 4 hours 

let boat speed = x
current speed =y

upstream speed = x-y
down stream speed = x+y
d/r=t
downstream
12/(x+y)=2
2x+2y=12
x+y=6.....1
upstream
8/(x-y)=4
4x-4y=8
x-y=4...........2
Add equation (1) & (2)
2x=10
x=5 mph
so y= 1

Boat speed = 5 mph, current speed = 1mph

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