Can someone help me please and thank you this is for science

Tissues that carry food water and nutrients throughout the plant

Little's law can be applied to any part of the store, such as a particular department or the checkout lines. the store owner determines that, during business hours, approximately 84 shoppers per hour make a purchase and each of these shoppers spend an average of 5 minutes in the checkout line. at any time during business hours, about how many shoppers, on average, are waiting in the checkout line to make a purchase at the good deals store?

Raul has one solution that is 20% acid by volume and one solution that is 50% acid by volume. he plans to mix together some of each solution to create 30 milliliters of a solution that is 40% acid by volume. how many milliliters of the 20% acid solution should raul use to create the 40% acid solution? can someone explain this to me? i know that the answer is 10 milliliters, but i don't know how to get it.