Final answer:
The width of the rectangle is 4 cm.
Step-by-step explanation:
To find the width of a rectangle, we need to divide the area by the length. In this case, the area is 36 square centimeters and the length is 9 centimeters. So, the width can be found by dividing the area by the length: 36 cm² ÷ 9 cm = 4 cm.