To find the sum of all the interior angles use the formula:
Sum = 180 (n-2) where n is the number of sides.
The sum of the interior angles for an 11 sided polygon is:
180 (11-2) = 180 x 91620 degrees.
Now to find the a single angle, divide the total by 11 ( number of sides)
1620 / 11 = 147.27 degrees. ( Round the answer as needed).