How many heptagons can be drawn by joining the vertices of a polygon with 10 sides?

Answer 1

Draw a decagon and label the vertices 1 - 10.

Regular heptagons cannot be formed.

1) line from 1 to 6

2) line from 2 to 7

3) line from 3 to 8

4) line from 4 to 9

4) line from 5 to 10

And so on until you have 20 heptagons.