1 3 2 6 4 9 8 12 16

Find a pattern

(2) 3*7-6= 15

3 540 720

Relationship "(n-2)* 180"

Nonagon internal angle sum: (9-2)* 180= 1260.

4 8

5 8

Teacher Wang, worker Liu, soldier Ding and worker Li.

7 3 142