Hello everyone! I hope you are all doing well today, and I am sorry I haven't been here in a while, but I guess that also shows that I may have a better time handling these questions in Precalculus now

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Anyway, I wanted to ask a question regarding the Set Theory which states:

At a picnic 12 people ate hamburgers, 20 ate frankfurters and 18 had ribs. Everyone had something to eat. Suppose 3 people ate both hamburgers and frankfurters, 6 people ate both frankfurters and ribs, 4 people had hamburgers and ribs, and 1 person ate all these types of food. How many people went on the picnic?

Thank you for all the help, and I hope that all of you are doing well.

-Norman