How to add and subtract fractions

You need to find the common denominator of all of the fraction and you also have to do whatever you did to the bottom to the top. So if you times the bottom by 2 you need to times the top by two. Then once you have that you can add and subtract! 

40°

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°