Respuesta :

[tex]\bf \textit{height of an equilateral triangle}\\\\ h=\cfrac{s\sqrt{3}}{2}\qquad \begin{cases} s=length~of\\ \qquad a~side\\ ------\\ s=12 \end{cases}\implies h=\cfrac{12\sqrt{3}}{2}\implies h=6\sqrt{3}\\\\ -------------------------------\\\\ \textit{area of an equilateral triangle}\\\\ A=\cfrac{s^2\sqrt{3}}{4}\qquad \begin{cases} s=length~of\\ \qquad a~side\\ ------\\ s=12 \end{cases}\implies A=\cfrac{12^2\sqrt{3}}{4}\implies A=36\sqrt{3}[/tex]

and of course as you already know the volume of the prism is just the area of the base times the length, namely A * 20.