Answer:
18 pi mm^2
Explanation:
First we find the area of the circle
A = pi r^2
A = pi (9)^2
A = 81 pi
The we find the fraction of the circle that is shaded
The degrees in a circle is 360
80 degrees are shaded
80/360 =2/9
Multiply the area by the fraction that is shaded
A shaded =2/9*81 pi = 18 pi