Answer:
6
Explanation:
You are increasing the amount of macaroni by 1/2 (or 50%), so you have to increase the amount of cheese by the same amount. Half of 4 is 2, so you add that together and get 6.
That is the way you would solve equations like this. However, in this SPECIFIC question, the amount of cheese is double the amount of macaroni, so you could just multiply the amount of macaroni (3 cups) by 2 to get your answer (6 cups). But this is a very specific situation!