Does the question actually ask how many diagonal does a 4-sided polygon, 5 sided polygon, 6-sided polygon, until 10 have?
We will try.
4-sided polygon = 2 diagonals
5-sided polygon = 5 diagonals
6-sided polygon = 9 diagonals
7-sided polygon = 14 diagonals
8-sided polygon = 20 diagonals
9-sided polygon = 27 diagonals
10-sided polygon = 35 diagonals