if the height and base are equal, that simply means that b = h, or h = b
and we know the area is 18 m²
[tex]\bf \textit{area of a triangle}\\\\
A=\cfrac{1}{2}bh\qquad
\begin{cases}
b=h\\
A=18
\end{cases}\implies 18=\cfrac{1}{2}\cdot h\cdot h\implies 18=\cfrac{h^2}{2}
\\\\\\
36=h^2\implies \sqrt{36}=h[/tex]
