If you mean a 15 sided polygon then its interior angles add up to 2340 degrees
360 degrees
1,080
Sum= 2340 Degrees A+
180
1260 degrees
1260 degrees
2340
1260 degrees
360 degrees
360 degrees.
180
There is no regular polygon with an interior angle of 20o. If the interior angle is 120o then there are six sides and the sum of the angles is 720o.