STEP 1: find side $ a $
To find side $ a $ use formula:
$$ r = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$After substituting $ r = 6 $ we have:
$$ 6 = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$ $$ \sqrt{ 3 } \cdot a = 6 \cdot 2 $$ $$ \sqrt{ 3 } \cdot a = 12 $$ $$ a = \dfrac{ 12 }{ \sqrt{ 3 } } $$ $$ a = 4 \sqrt{ 3 } $$STEP 2:
The radius of the circumcircle is equal the side of the hexagon. $$ R = 4 \sqrt{ 3 } $$