Answer:
30 cm²
Explanation:
The shaded area is the difference between the area of the rectangle and the area of the triangle.
The area of the rectangle is ...
A = LW = (12 cm)(4 cm) = 48 cm²
The area of the triangle is ...
A = 1/2bh = 1/2(9 cm)(4 cm) = 18 cm²
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The shaded area is the difference ...
rectangle area - triangle area = 48 cm² -18 cm² = 30 cm²
The area of the shaded region is 30 square centimeters.