Eli wants to combine 0.5 gallon of a 10% acid solution with some 35% acid solution to make a 15% acid solution. Which equation can you use to determine how many gallons of the 35% acid solution Eli should add?

Let x = number of gallons of the 35% acid solution Eli should add. The equation would be

0.5 gal (0.1) + x gal (0.35) = (0.5 + x) (0.15)

This would be the equation to find the answer.

Solving for x,

X = 0.125 gallons