If her original measurements for that recipe feeds 6 people, then write this equation, 6p = 72, to represent the amount of people it will feed. 72 divided by 6 is 12. The thing is, 12 isn't your answer. In the actual problem, it states that a quarter cup of mayonnaise is necessary to feed 6 people. So multiple one-fourth by 12. (If you don't know how to do that, just divide 12 by 4.)
As a result, your final answer should be 3 cups of mayonnaise.