Solution A is 30% alcohol and solution B is 60% alcohol. How much of each is needed to make 80 liters of a solution that is 45% alcohol?

We need 80 liters of 45% alcohol

We have 30% alcohol and 60% alcohol.

This is relatively easy. We need equal amounts of each.

There fore we mix 40 liters of 30% alcohol and 40 liters of 60% alcohol.