Answer: 80°
Explanation:
We know that the sum of all angles in a polygon having n sides is given by :

For octagon , n= 8
Then, the sum of all angle sin octagon =



It is given that , The sum of the measures of seven angles of an octagon is 1000 degrees.
Then, the measure of the eighth angle = Sum of all angles - 1000°
= 1080° - 1000° =80°
Hence, the measure of the eighth angle is 80° .