A pool is filled by two pipes. It takes the first pipe 2 hours more and the second pipe 4 hours more to fill it than both pipes at the same time.
The book says that the first pipe fills the pool in 5 hours and the second one in 7.5 hours, so I think I did something wrong.
Anyway, here's what I did:
let z be the time it takes both pipes to fill the pool
let x be the speed of first pipe
let y be the speed of second pipe
So I get, that
Which solves for x=4,8 and y= 6,8
I need some hints please.