This is the statement m

Step-by-step explanation:

First we must know that the sum of all the exterior angle of all polygons is 360°.

Measure of each angle of a polygon = 360°/total sides of the polygon

Since a regular nonagon has 9 sides, the measure of each angle of a polygon is expressed as thus;

Measure of each angle of a polygon  = 360°/9

Measure of each angle of a polygon  = 40°

Hence the measure of an exterior angle x of a nonagon is 40°