You are mixing light yellow paint, and want to do it by mixing yellow paint with white paint. You mix a total of in the ratio . You then discover that you should have mixed it in the ratio instead. What can you do to fix the ratio?
You already mixed the paint in the ratio . That means you have 7 parts in total. You had dL of paint, which means there are per part. If you then add dL of yellow paint to the mix, you will have parts in total, where 3 of the parts are yellow and 5 of the parts are still white. That makes the mixing ratio , just like you wanted.