Answer:
30.683 (I didn't know how many decimal places were needed so I went with 3)
Explanation:
All you have to do is find the area of the rectangle: base x height and then subtract the area missing from the semicircle. The area of a semicircle is 1/2pi x radius^2. So if you plug in the numbers, it would look like this: (9 cm x 4.5 cm) - (1/2pi x (2.5)^2).
Hope this helps, it should be correct. :)