Systems of Equations

Question

Nicolas mixes three solutions of acid with concentrations of 10%, 15%, and 5%. He wants to make 30 L of a mixture that is 12% acid and he uses four times as much of the 15% solution as the 5% solution. How much each of the three solutions must he use?

Answer 1

x represents amount of 5%

4x represents the amount of 15%

30 - 5x represents the amount of 10%

 

0.10(30 - 5x) + 0.05x + 0.15(4x) = 0.12(30)

 

Can you solve for x?