A chemist needs 30mL of a 12% acid solution for an experiment. The lab has available a 10% solution and a 25% solution. How many milliliters of the 10% solution and how many milliliters of the 25% solution should the chemist mix to make the 12% solution?

parts of 10% soln, xparts of 25% soln, ytotal soln, x+y =30{x(0.1) + y(0.25)}/(x + y) = 0.12...eqn 1x + y = 30...eqn 2from eqn 2...=》 x = 30-y subst for x in eqn 1...=》 {(30-y)(0.1) + y(0.25)}/ 30-y+y = 0.12=》 (3-.1y+.25y)/30 =0.12=》 3+.15y = 3.6=》 .15y = .6=》 y =4using x = 30 - y = 26ans26ml of 10% soln 4ml of 25% soln