This problem belongs to permutation and combination.

Let me give you an example: 8 students, choose 5 students to stand in a row. How many different standing positions are there?

First place: 8 students can stand. There are eight situations.

Second place: Because one classmate stood in the first place, there are seven other students who can stand. There are seven situations.

Third place: There are six situations in the competition. ...............

Fourth place: There are five situations in the competition. ...............

Fifth place: There are four situations in the class. ...............

The station method of * * is the product of these five numbers.

8X7X6X5X4

=56X 120

=6720 (species)

Think for yourself! It should be understandable.