We know that the tub needs 20 gallons to fill, so our equation will be
something something = 20
Now, we know that it fills at 2.5 gallons PER MINUTE. That per minute is very important because it tells us how many gallons are filled after a certain amount of time.
So, we write the equation as 2.5x = 20. This is because our x (the unknown) is time, and it is filling up 2.5 gallons per time. So, divide 2.5 on each side, and we get 8 minutes as our answer.
