To find side $ a $ use formula:
$$ h = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$After substituting $ h = 36 $ we have:
$$ 36 = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$ $$ \sqrt{ 3 } \cdot a = 36 \cdot 2 $$ $$ \sqrt{ 3 } \cdot a = 72 $$ $$ a = \dfrac{ 72 }{ \sqrt{ 3 } } $$ $$ a = 24 \sqrt{ 3 } $$