Answer:
7.7 ft
Explanation:
The third longest side is also the second shortest side.
The 14 ft side of quadrilateral ABCD corresponds to the 6 ft side of quadrilateral EFGH.
14/6 = 18/x
7/3 = 18/x
7x = 18 * 3
7x = 54
x = 54/7
x = 7.7
Answer: D. 7.7 feet