Answer:
18 cm²
Step-by-step explanation:
The area labelled A is a triangle.
The area (A) of a triangle is calculated using the formula
A = [tex]\frac{1}{2}[/tex] bh ( b is the base and h the height )
here b = 9 and h = 4 ( the same height as the rectangle ), thus
A = [tex]\frac{1}{2}[/tex] × 9 × 4 = [tex]\frac{1}{2}[/tex] × 36 = 18 cm²