Question 260932
Since all sides are equal, the perimeter is 4s. So we have the inequality
{{{13 <= 4S <= 48}}}
step 1 - divide all parts by 4 to get
{{{13/4 <= S <= 12}}}
If assume only integers, then the set is
S={4, 5, 6, 7, 8, 9, 10, 11, 12}