Answer:
6:1
Explanation:
For every 3 cups of ketchup, you need 1/2 cup of mustard, and since the ratio is asking you for a ratio in cups, you need to multiply both 3 and 1/2 by 2, so you can get the 1/2 to a full cup, giving you the ratio of 6 cups of ketchup to 1 cup of mustard.