The formula for the perimeter (P) of a square with sides length S is:
P = 4S. Divide both sides by 4 to find the length of a side.
P/4 = S.
In this problem we're given a maximum P (225 inches). So S must be no bigger than a length that will result in 225 inches. That is:
S <= P/4 Which is S <= 225/4. That gives: S <= 56.25 inches.
Sides can be any length equal to 56.25 inches, or smaller than 56.25 inches.