To find side $ a $ use formula:
$$ r = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$After substituting $ r = 85 $ we have:
$$ 85 = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$ $$ \sqrt{ 3 } \cdot a = 85 \cdot 2 $$ $$ \sqrt{ 3 } \cdot a = 170 $$ $$ a = \dfrac{ 170 }{ \sqrt{ 3 } } $$ $$ a = \frac{ 170 \sqrt{ 3}}{ 3 } $$