Answer:
Step-by-step explanation:
You need to remember that formula for calculate the area of a rectangle:
Where "l" is the lenght and "w" is the width.
You know that "x" represents the width of the doghouse, its rectangular base has an area of 21 square feet () and its length is 4 feet more than its width ()
Then, substituting into the formula, you get:
Simplifying, you get the following that can be used to determine the possible dimensions of the base of the doghouse: