Question

A polygon with nine sides has the following interior angle measurements: 52°, 244°, 144°, 70°, 81°, 272°, 97°, 200°, and x° What is the value of x?

Answer 1

We know, sum is equal to 1260 in polygon with 9 sides, 
so, 52 + 244 + 144 + 70 + 81 + 272 + 97 + 200 + x = 1260
1160 + x = 1260
x = 100

In short, Your Answer would be 100

Hope this helps!

Answer 2

The first thing that would help you the best is to know the sum of the angles of a nine sided polygon. 

The formula for finding the sum of interior angles for any polygon is (n-2)*180
where "n" is the number of sides.

So, plug in 9 for n.

9-2 = 7
7 * 180 = 1260
Now , subtract all the known interior angles from 1260.
After subtracting all the known interior angles from 1260 you should be left with 100.

This means that the value of x is equal to 100°