check the picture below
notice, is a "square" pyramid, so its base is a square,if one edge is 10, all are 10
[tex]\bf \textit{volume of a pyramid}\\\\
V=\cfrac{1}{3}Bh\qquad
\begin{cases}
B=\textit{base area}\\
h=height\\
------\\
B=10\cdot 10\\
h=12
\end{cases}\implies V=\cfrac{1}{3}(10\cdot 10)12[/tex]
