Mixture problem

You need a 80% alcohol solution. On hand, you have a 1040 mL of a 85% alcohol mixture. How much pure water will you need to add to obtain the desired solution? A) Write an equation using the information as it is given above that can be used to solve this problem. Use a as your variable to represent the amount of pure water you need to use. Equation: B) You will need mL of pure water to obtain mL of the desired 80% solution