Answer: 4 feet < Length < 21 feet
Explanation:
From the question, the length of the rectangular fence is 4 feet more than its width and the perimeter of the fence is less than 42 feet. The range of the lengths of the fence will be:
Length is greater than 4 feet (4 feet more than the width. This means that the length must be at least 4 feet) and less than 21 feet i.e the length must be less than 1/2 of the perimeter which is 42/2 = 21. Therefore, the answer will be:
4 feet < Length < 21 feet