HELP PLEASEEEE

Tammy has a rectangular rug with an area of 21 square feet. The rug is 4 feet longer than it is wide. Which equation can be used to determine the length and the width of the rug?

A.
21 = 4w^2

B.
21 = w^2 + 4w

C.
21 = w^2 – 4w

D.
21 = w^2 + 4