Answer: 123 square feet
Step-by-step explanation: The question is a little odd, but I can break it down easily. It wants us to find the area of a three foot border around his room.
First, the whole area of his room is 20 x 24 = 480
Next, we have to make the measurements 3 feet smaller on each wall, so 17 x 21 = 357
Finally, to find the area of the border, we simply do 480 - 357 = 123
He needs to buy 123 square feet of carpeting
Hope this helps!
Answer:

Step-by-step explanation:
To simplify polynomials, find the like terms which look and sound the same then combine the coefficients of each to simplify.

Congruence transformation results to a perimeter of any polygon that is the same as the original dimensions and shape. In this case, this is similar to translation where all dimensions, angles are retained constant. The answer to this problem hence is B