Answer: x=8
Step-by-step explanation:
the sum of the interior angles of a quadrilateral is 360 (number of sides-2 * 180)
so

To find the formula to find radius, solve for r using the formula for circumference.
to solve:
1. divide each side by 2

2. you get
r = c/2
The 4th term is 135
n-1
you get it by using the formula Tn= ar <span />
Attached the solution and work.