Consider the following problem:
How much antifreeze which is 30% alcohol must be removed from a 48-ounce container and replaced with water to make 48 ounces of a solution which is 20% alcohol?
Is there some visual way to to understand these types of problem?
I don't know what you mean by a visual way. I could draw a picture of a bucket that has 48 oz of mix, divided into 30% alcohol and 70% other, but I don't see how that helps. How much alcohol is in the bucket to start? How much do you want in the bucket at the end? Remove the correct fraction of the total liquid to make the alcohol content what you want. Refill. Done.