Answer:
2a. The length and width can be defined by the expressions (x-6) and (x+3).
2b. For x=12, length and width can be 6 units and 15 units. Area will be 6·15 = 90 units².
Step-by-step explanation:
2a. You have correctly factored the polynomial. You need to make use of those factors to answer the question asked. (Factoring is a means to get to the answer; the factoring is not the answer.)
2b. Again, you have to pay attention to the question(s) asked. Filling x=12 into the factors you found lets you use those to find the length and width asked for. You can evaluate the original polynomial to find the area (as you have), but you are asked to make use of the Part A results to do so. A number by itself doesn't answer a question that asks for three numbers.
For x=12,
... x - 6 = 6 . . . . length or width (in units)
... x + 3 = 15 . . . . width or length (in units)
... area = length·width = 6·15 = 90 . . . . units²
