Take two groups as an example: 1, 12, with 7 people as one group and 5 people as the other group, c 12, 7*c5, 5.

2. Seven people were selected from12 as Group A, and the other five people were selected as Group B, C12,7 * C5,5.

3. Choose 7 people from 12 as a group, and 5 people as a group, and then arrange Group A and Group B: c 12, 7*c5, 5*a2, 2.

4. Six people were selected from12 as group A, and the other six people were selected as group B, C12,7 * C5,5.

5. 12, select 6 people as a group, and the remaining 6 people as a group, c12,6 * C6,6. The three groups are the same.

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