Two water pumps are filling a pool. one of the pumps is high power and can fill the pool 5 hours before the other can do. however, they both working together can fill half of the pool in 3 hours. in how many hours the high power pump can fill the pool

L = hours for the slower pump to fill the pool

L - 5 = hours for the high power pump, since it can do it in 5 hours less.

since the slower pump takes L hours, the faster pump takes then L - 5 hours.

we know both pumps together take 3 hours to do half of the pool, so that means that to fill up the whole pool it takes them 6 hours.

since the slower pump can do it alone in L hours, in 1 hour it has done 1/L of the whole thing.

likewise, since the faster pump can do it in L-5 hours, in 1 hour alone it has done 1/(L-5) of the whole job.

now, we can't use L = 2, because, the whole job by both is done in 6 hours, there's no way the slower pump can do it in less than that, so L = 15.

now if L = 15, then L - 5 = 10.