Answer:
z = 15
Explanation:
The sum S of the interior angles of a regular polygon is given by the formula
S = (n-2) x 180 where n is the number sides
Here n = 9
So S = (9-2) x 180 = 7 x 180 = 1,260
There are 9 interior angles and each angle is (5z + 65)
So the sum of all 9 interior angles = 9 (5z + 65)
= 45z + 585
Set these equal to each other and solve for z
45z + 585 = 1260
45z = 675
z = 675/45 = 15