appetizers survey: evaluating results

A Restaurant hired Dennis Goldstein to determine what kind of appetizers customers liked. He surveyed 100 people, with the following results: 78 liked shrimp coctail, 56 liked mozzarella sticks, and 35 liked both shrimp cocktail and mozzarella sticks. Every person interviewed liked one or the other or both kinds of appetizers. Does this result seem correct? Explain your answer.

Help please

What does the question mean when it asks whether or not the reported results "seem correct"? I mean, either the guy reported the results accurately, or else he didn't. But how would one be supposed to evaluate this, just from the numbers?

Please clarify. Thank you!

Eliz.

Draw a venn diagram.

78+56-35 = ?