We know that the perimeter is the all the sides added up together. Generally, you have 
, where l is length and w is width.
For a square, all sides are of the same length, so you can write
, where x is any side.
If the smallest perimeter is 14, then
, so x is 3.5. If the largest perimeter is 72, then 
, so x is 18.
Therefore, you have 3.5 ≤ x ≤ 18.
For a square, all sides are of the same length, so you can write
If the smallest perimeter is 14, then
Therefore, you have 3.5 ≤ x ≤ 18.