Question 909520
We subtract for the drain pipe.
 We are doing 3/4 of the job since the pool is 1/4 filled

x/15-x/24=3/4
x/15-x/24=3/4
24x/360-15x/360=3/4
8x/120-5x/120=3/4
3x=3/4*120
3x=3*30
x=30 hours
check
10/15-10/24=3/4
720/360-450/360=3/4
240/360-150/360=1/4
90/360=1/4
1/4=1/4
ok