How to find the number of sides of a polygon when given the interior angle sum

Given:

Sum of interior angle

To find:

Number of sides of a polygon

Solution:

Using sum of interior angles formula:

where "S" is the sum of interior angels and "n" is the number of sides of a polygon.

Divide by 180° on both sides.

Cancel common factor 180°.

Add 2 on both sides.

Switch the sides.

Therefore number of sides of a polygon is .

1) the property is   ixi = a ⇔x = a   o x = -a

4(x-5)+3= 15⇒4x-20+3 = 15⇒4x-17= 15⇒4x = 15+17⇒4x = 32⇒x =32/4= 8

4(x-5) +3= -15⇒4x-20 +3 = -15⇒4x-17= -15⇒4x =-15+17⇒4x = 2⇒x =2/4= 1/2

the values are x =8 and x = 0,5