Upstream downstream JuniorSolutionLet the speed of the curre

Upstream, downstream. Junior

Let the speed of the current be x mph.
[Note x should be less than 15 mph, for otherwise theboat cannot move
when gotupstream.]
Downstream speed = x + 15. (sum of the speeds)
Upstream speed = 15-x, (difference of the speeds)
Now we have 12/(x+15) = 9/(15-x) or
4(15-x) = 3(x+15)
so 7x = 15 , x = 15/7 mph.
You did completely wrong , try to think about it.