8.2. If a class of 30 people is seated in a cinema hall, then in any case, at least two classmates will end up in the same row. If the same is done with a class of 26 people, then at least three rows will be empty. How many rows are there in the hall?
Answer: 29.

There are no more than 29 rows in the hall. Otherwise, a class of 30 students can be seated with one student per row. On the other hand, if a class of 26 students is seated with one student per row, at least three rows will be empty, which means there are no fewer than 29 rows.

Comment. An answer without justification - 2 points.