the first fish tank has 100 gallons of water and 1 gallon is removed every hour which makes 100-h
the second tank has 40 gallons in it and 2 gallons are added every hour which makes 40+2h
after 20 hours the second tank will have more gallons than the first tank
this means that 40+2h would be greater than 100-h since it's also asking you "After how many hours will the first tank have less water than the second?"
