Question 467520
Let Jim's hose take x hours
it does 1/x of job in 1 hour

Bob's hose will take 0.8x hours  ( 20 percent less)
it does 1/0.8x of the job in 1 hour

together they take 18 hours
so they do 1/18 of the job in 1 hour

1/x + 1/0.8x = 1/18

1/x + 1.25/x = 1/18

multiply by 18x

18+18*1.25 = x
x= 40.5 hours Jim's hose
Bobs hose will tale 0.8*40.5 = 32.4 hours