What is the measure of one angle of 14 sided regular polygon?

The sum of the angles in an N sided polygon is 180°(N - 2)
The angle of a single angle then would be:

180°(N - 2)/N
= 180° - 360°/N

So in the case of a 14 sided regular polygon, a single angle would be:

180° - 360° / 14
= 180° - 180° / 7
= 6/7 * 180°
= 1080°/7
≈ 150.286°