so hmm notice the picture below
is a "square" pyramid, thus, the base is a square, all sides are the same
now, we know the volume is 75 and one side is 5
thus [tex]\bf \textit{volume of a pyramid}\\\\
V=\cfrac{1}{3}\cdot Base\cdot height\qquad
\begin{cases}
Base=length\cdot width\\
\qquad\qquad 5\cdot 5=25\\
V=75
\end{cases}\\\\\\ 75=\cfrac{1}{3}\cdot 25\cdot h[/tex]
solve for "h" or height