Hello!
Here's a break down of 8. and 9.
----------question 8:
For number 8., it asking you what is the sum of the Interior Angles of a polygon with 12 sides.
We know that a dodecagon is a 12-sided polygon with 12 angles and 12 vertices.
We also know that when you add up the angles it needs to equal a number.
When added up all the interior angles (angles within a polygon) of a polygon of 12 sides we get 1800°.
So the answer for 8. is 1800°
--------------question 9:
A quadrilateral has interior angles of 85°, 105°, and 120°. What is the measure of the 4th angle.
Remember that all quadrilaterals have 4 angles that add up to 360°.
So first: Add the given interior angles;
You get: 310
Next subtract the 310° from 360°
You get 50°
The measure of the 4th angle is 50°.
------------------------
I hope this helps you,
Have a great day!!