To find side $ a $ use formula:
$$ r = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$After substituting $ r = 89 $ we have:
$$ 89 = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$ $$ \sqrt{ 3 } \cdot a = 89 \cdot 2 $$ $$ \sqrt{ 3 } \cdot a = 178 $$ $$ a = \dfrac{ 178 }{ \sqrt{ 3 } } $$ $$ a = \frac{ 178 \sqrt{ 3}}{ 3 } $$