Answer:
The polygon has 9 sides
Explanation:
we know that
A regular polygon has equal length sides and equal interior angles
step 1
Find the measure of the interior angle
Remember that
The interior angle plus the exterior angle must be equal to 180 degrees (form a linear pair)
Let
x ----> the measure of each interior angle in the regular polygon
so

solve for x

step 2
Find the number of sides of the regular polygon
we know that
The measure of each interior angle in a regular polygon is given by the formula

where
n is the number of sides of the polygon
substitute the given values

solve for n

therefore
The polygon has 9 sides