A rectangle has all angles and all sides equal to each other.

A hexagon as 6 sides.

A regular octagon has 8 sides of equal length.

A rhombus and a rectangle are irregular polygons.

180

90

360

540

paralellogram

square

rhombus

kite

90

120

140

150

$\frac{n\left(n+3\right)}{2}$ 

$\frac{n\left(n-3\right)}{2}$

$\frac{n+\left(n-3\right)}{2}$

$\frac{n+\left(n+3\right)}{2}$