Question

You want to mix a 5% blue dye with a 20% blue dye to make a 12% blue dye. The function y =100(0.05)+x(0.2)/100+x gives the concentration y of blue dye after you add x mL of the 20% dye to 100 mL of the 5% dye. How much of the 20% dye must you add to get a dye that is 12% concentrated?