We are given with two solutions: 10% salt and 25% salt solutions. We are in need of 5 gallons of 20% salt. The linear equations are 0.10 x + 0.25 y = 5 *0.20 and x + y = 5 where x is the volume needed of the 10 % salt solution and y is the volume needed of the 25 % percent solution. Solving the two equations simultaneously, x is equal to 1.67 gallons and y is equal to 3.33 gallons.