A regular polygon having an interior angle measure of 168o has 30 sides and is called a triacontagon.
Only if the polygon is "regular".
Only when it is a regular polygon that all interior angles are of equal measure
A pentagon (five sided regular polygon) has interior angles of 108°.
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.
The measure of each interior angle of a fifteen sided regular polygon, a pendedecagon, is 156o.
A 13 sided regular polygon
The interior angle of an octdecagon, an 18 sided regular polygon, is 160o.
A regular polygon with 4 sides is a square. The measure of any interior angle of a square is 90 degrees.
Only if the polygon is a "regular" one.
A regular hexagon.
Only when the polygon is a regular convex polygon. Such as an equilateral triangle, or a square, or a regular pentagon.