A 3% solution of sulfuric acid was mixed with an 18% solution of sulfuric acid to produce an 8%solution. How much 3% solution and how much 18% solution were used to produce 15 L of 8% solution?

Let the number of Liters of 3% solution==T

Then the number of Liters of 18% solution ==15 - T

0.03T + 0.18[15 - T]==0.08 * 15

0.03T + 2.7 - 0.18T ==1.2

0.18T - 0.03T ==2.7 - 1.2

0.15T ==1.5

T ==1.5 /0.15 ==10 Liters of 3% solution.

15 - 10 ==5 Liters of 18% solution.