To find side $ a $ use formula:
$$ h = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$After substituting $ h = 240 $ we have:
$$ 240 = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$ $$ \sqrt{ 3 } \cdot a = 240 \cdot 2 $$ $$ \sqrt{ 3 } \cdot a = 480 $$ $$ a = \dfrac{ 480 }{ \sqrt{ 3 } } $$ $$ a = 160 \sqrt{ 3 } $$