Note: In the case of decreasing 1 boat and increasing 1 boat, the number of people per boat after decreasing 1 boat is 3 more than that after increasing 1 boat.

2× 6 = 12 (person)

Note: After adding 1 boat, each boat will take 6 people, which is 2 more boats than after reducing 1 boat. If 1 boat is reduced and each boat takes 6 people, 12 people will not be able to row.

12 ÷ 3 = 4 (article)

Note: The extra 12 people are assigned to other ships, so the number of people on each ship after reducing 1 ship is 3 more than that after increasing 1 ship, and it is concluded that there are 4 ships after reducing 1 ship.

4× 9 = 36 (person)

There are 36 students in Class One.