Answer:
8 < x < 16
Explanation:
Consider an angle slightly less than 180 between the 4 and 12 ft sides. The measure between the 2 end points is slightly less than the total of the two sides. So the greatest length is 16.
Consider an angle slightly more than 0 between the 4 and 12 ft sides. The measure between the 2 end points is slightly more than the difference between the two sides. So the lowest length is 8.