If the perimeter of a septagon (in which all sides are equal) is , then the length of one side will be one seventh of this expression. 

To find one seventh, the value must first be simplified and then divided by 7. 

When this is divided by 7, the result is:

This value is thus the length of one side of the septagon. 

The number of degrees in an internal angle of a regular polygon can be solved using the following equation where n equals the number of sides in the polygon:

The measure of an interior angle of a regular polygon can be determined using the following equation where n equals the number of sides:

The answer can be more clearly seen by extending  to a ray :

Note that angles have been newly numbered.

 and  are exterior angles of a (five-sided) regular pentagon in relation to two parallel lines, so each has a measure of .  is a corresponding angle to , so its measure is also .

By angle addition, 

The answer can be more clearly obtained by extending the top of the two parallel lines as follows:

Note that two angles have been newly labeled.

 is an interior angle of a regular heptagon and therefore has measure

By the Isosceles Triangle Theorem, since the two sides of the heptagon that help form the triangle are congruent, so are the two acute angles, and

 is supplementary to , so 

The answer can be more clearly seen by extending the lower right side of the heptagon to a ray, as shown:

Note that angles have been newly numbered.

 and  are exterior angles of a (seven-sided) regular heptagon, so each has a measure of .  is a corresponding angle to  in relation to two parallel lines, so its measure is also .

By angle addition, 

The sum of the degree measures of the angles of Quadrilateral  is 360, so

Each interior angle of a regular pentagon measures 

,

which is therefore the measure of .

It is also given that  and , so substitute and solve:

The sum of the degree measures of the angles of Quadrilateral  is 360, so

.

Each interior angle of a regular pentagon measures 

,

which is therefore the measure of both  and .

 and  form a linear pair, making them supplementary. Since ,

.

Substitute and solve:

The total of the degree measures of any eight-sided polygon is

.

In an arithmetic sequence, the terms are separated by a common difference, which we will call . Since the greatest of the degree measures is , the measures of the angles are

Their sum is 

The least of the angle measures is 

The correct choice is .

The sum of the angles in a polygon can be found using the equation below, in which t is equal to the total sum of the angles, and n is equal to the number of sides. 

Therefore, the equation for the sum of the angles in a 9 sided polygon would be:

Therefore,  of the total sum of degrees in a 9 sided polygon would be equal to 180 degrees.