The atomic mass of hydrogen-1 is 1. 008 and the atomic mass of helium-4 is 4. 3. Find the difference in grams between 4 moles of hydrogen and one mole of helium.

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.