10 hours : 10*5 = 50 gallons
15 hours: amount in pool + hose * 5 hours - drinking*5 hours
= 50 +5*5 - 2*5 = 50+25-10 = 65 gallons
100 = amount in pool + 1st hose*hrs - drinking*hrs + 2nd hose*hrs
hrs is after the 15 hours already filling the pool
100 = 65 gallons + 5*h -2h +4h
combine like terms
100 =65 +7h
subtract 65
35 = 7h
divide by 7
h=5
add the 15 hours before
20 hours to fill the pool
1pm + 20 hrs
24 hrs would be 1pm again so subtract 4 hours
9 am the next day