Question 1010462
First of all, rate times time equals distance, or rt=d.
Next, let's call the rate of the boat in still water, r.
Then, let's call the rate of the current, c.
Going upstream we have
6(r - c) = 30  OR  r - c = 5
Goind downstream we have
6(r + c) = 72  OR  r + c = 12
We add the second set of equations and get
2r = 17
r = 8.5 mph
c is then 3.5 mph.