Question

I need the answer for 9

Answer 1

Sum of Interior Angles = (n-2) × 180°
so you can use this to find out how many sides of this polygon

 (n-2) × 180° = 1800
 n - 2 = 10
      n = 12

this polygon has 12 sides

Answer 2

The sum of the measures of the angles of a polygon of n sides is 180(n - 2).

Set that expression equal to 1800 and solve for n, the number of sides.

180(n - 2) = 1800

Divide both sides by 180

n - 2 = 10

Add 2 to both sides

n = 12

The polygon has 10 sides.