How much 20% solution needs to be added to a 60% solution to make 400 ml of a 40% solution

Let be the volume of 20% solution, the volume of the 60% solution. We want a total volume of 400 mL in the final mixture, so

Each mL of either solution will contribute a corresponding concentration, and in the final mixture we want the 400 mL to have a 40% concentration, which means we should also have

Solve the system and we get .

(0.2)+(-8)=0.3+-3+0.3m is the equation i guess? ?

step-by-step explanation: