For this case we have the following solution. First, let's give the variable a name: Let x = gallons of water to be added For the 10% solution we have: 0.1 * 8 = 0.8 Then, for 5% we have: (0.8 / x + 8) = 0.05 Rewriting: (0.8 / x + 8) = (5/100) Answer: An equation can be used to find x, the humber of gallons of water he should add is: (0.8 / x + 8) = (5/100) (option 2).
