Answer:
6.
1 table seats 5 students
2 tables seat 8 students
3 tables seat 11 students
4 tables seat 14 students
5 tables seat 17 student
Each new tables allows 3 more students to have a seat.
7.
Each additional table does not have seats for 5 students because the side of it is pressed against another table, so a student cannot sit there.
