The formula to calculate area for a rectangle is length * width.
The length is 8.5 cm and the width is 4.5
Simply multiply 8.5 * 4.5 to determine the area of the rectangle
8.5 * 4.5 = 38.25
Answer
The area of the rectangle would be 38.25
Additional information
If you were to find the area of a square, you would apply this same concept in order to find the area.
Additionally, if you were to calculate the area of a Parallelogram, you would determine the area by multiplying base * height.