[tex]\bf \textit{area of a square}\\\\ A=s^2~~ \begin{cases} s=length~of\\ \qquad a~side\\[-0.5em] \hrulefill\\ A=56.25 \end{cases}\implies 56.25=s^2 \implies \sqrt{56.25}=s\implies 7.5=s[/tex]
now, the perimeter of it, is simply the sum of all its sides' lengths, so, recall a square has four equal sides, thus the perimeter is then 7.5+7.5+7.5+7.5.
