Area of circle = Pi x r*2
If diameter is 18, radius is 9.
Area = pi (3.14) x r*2 (9*2 = 81) .. 3.14 x 81 = 254.34 sq cen = total area of circle.
A circle is 360 degrees, the shaded area is 270 degrees. the shaded area is 3/4 (270/360) of the area of the circle.
254.34 x 3/4 = 190.755 sq cen
Hope this helps