Answer: 297 mm²
Explanation:
First, we know that in a rectangle, the opposite sides are always equal to each other, so we can know that the base of the rectangle/triangle is equal to 22 mm.
Second, let's find the area of the rectangle and the triangle. The area of the rectangle is just 22 mm times 18 mm, which is 396 mm². The area of the triangle is 0.5 times the height times the base, which is 0.5 × 9 mm × 22 mm = 99 mm².
Therefore, we can find out the shaded area by subtracting the area of the triangle from the area of the rectangle:
396 mm² - 99 mm² = 297 mm²