Only if the polygon is a regular quadrilateral.
A regular polygon
a "regular" polygon
Each exterior angle will measure 360/18 = 20.0 degrees
A regular polygon.
That would be a regular polygon.
Only if the polygon is "regular".
A regular polygon having an interior angle measure of 168o has 30 sides and is called a triacontagon.
A 13 sided regular polygon
Only when the polygon is a regular convex polygon. Such as an equilateral triangle, or a square, or a regular pentagon.
If the measure of an interior angle of a regular polygon is 140o, the polygon is a nonagon (sometimes called an ennagon) having 9 sides.
A regular polygon has all sides of equal length, and all angles of the same measure. An irregular polygon does not fulfil these requirements.