[tex]\bf \textit{volume of a pyramid}\\\\
V=\cfrac{1}{3}Bh\qquad
\begin{cases}
B=\textit{area of the base}\\
h=height\\
----------\\
h=12\\
V=236
\end{cases}\implies 236=\cfrac{1}{3}B(12)
\\\\\\
3\cdot 236=12B\implies \cfrac{708}{12}=B\implies 59=B[/tex]
now, is a square pyramid, like the picture below, so the base is just a square, so B = length * width, thus
[tex]\bf B=length\cdot width\quad
\begin{cases}
length=x\\
width=x\\
B=59
\end{cases}\implies B=x\cdot x\implies B=x^2
\\\\\\
59=x^2\implies \sqrt{59}=x[/tex]
