You work in a lab. You need a 15% acid solution for a procedure, but your supplier only sells a 10% solution and a 30% solution.
You must mix the 10% solution with 30% solution to make your own 15% solution. You need 10 liters of the 15% acid solution. How many liters of 10% solution and 30% solution should you mix together?
I'm not really an expert on chemistry but here is a link that I believe might be helpful. https://socratic.org/questions/suppose-you-work-in-a-lab-and-you-need-a-15-acid-solution-to-conduct-a-certain-t