Suppose there are x people who like to eat, and no one likes to eat here.

According to the principle of tolerance, the total number of people = 30+28+20-15-18-13+x = 32+x people.

So there are eight people who like to eat, so the person who only likes to eat fish is 30-15-13+8 =10.

Only meat lovers are 28- 15- 18+8=3 people.

Only people who like to eat 20- 13- 18+8=-3 people.

So the topic is still problematic.

You see, 20 people like to eat, 18 people like to eat fish, so two people don't like to eat fish, 13 people like to eat meat, so at least 1 1 people like to eat, which makes it easy to push out the contradiction.