Question

Yuri makes his own citrus vinaigrette salad dressing. He likes the dressing best if it contains 40% fruit juice. He has a bottle of dressing mixture that contains 60% juice and 3 cups of dressing that contains 20% juice. How much of the dressing mix with 60% juice should Yuri add to the dressing mix with 20% juice to get the dressing he prefers with 40% juice? Show your work.