6 gallons since the gallons of water is divided by too since the initial value added 1/2 so the number of gallons is divided by too and added to the original amount of gallons so i believe your answer will be 6 gallons
So first what you are going to do is divide synthetically your root aka factor into your given equation. Then you are going to kind of guess ands check to find the other factor by synthetically dividing what you have left which should be
x^2 +2x +1 by -5, 5 (to make sure there is no multiplicity), 1, and -1 until you get zero in your remainder spot. The number you used to divide will be your other root.
10 because there is 4 zero's behind the one. Hopes this helps!! :)