Sam is covering her rectangular pool for the winter. The area of the cover is x² + 13x + 42 ft². The length of the cover is (x + 7) feet.

A. What is the width of the cover? Make sure to include the unit of measurement.

B. How did you find the width? Explain in complete sentences.

C. If x = 4, what is the area of the pool cover?
please show your work