To solve the problem, we need to find the area of Marlena's living room floor that is not covered by the rug.

Step 1: Find the area of the living room floor

The living room floor is a square with a side length of 12 feet. $\text{Area of the floor} = 12 \times 12 = 144 \text{ square feet}$

Step 2: Find the area of the rug

The rug is a square with a side length of 9 feet. $\text{Area of the rug} = 9 \times 9 = 81 \text{ square feet}$

Step 3: Find the area not covered by the rug

The area not covered by the rug is the difference between the area of the floor and the area of the rug. $\text{Area not covered} = 144 - 81 = 63 \text{ square feet}$

Therefore, the correct answer is 63 square feet.

Would you like further details or explanations?

Related Questions

1. How do you calculate the area of a rectangle?
2. What happens if the rug and floor have different shapes?
3. How would the problem change if the rug wasn't a square?
4. What if we had a circular rug on a square floor—how would you calculate the uncovered area?
5. Can you calculate the area covered if the rug was rotated?

Tip

Always make sure to subtract smaller areas from larger ones to find the uncovered space.