STEP 1: find side $ a $
To find side $ a $ use formula:
$$ d = 2 \cdot a $$After substituting $ d = 30 $ we have:
$$ 30 = 2 \cdot a $$ $$ a = \dfrac{ 30 }{ 2 } $$ $$ a = 15 $$STEP 2: find perimeter $ P $
To find perimeter $ P $ use formula:
$$ P = 6 \cdot a $$After substituting $ a = 15 $ we have:
$$ P = 6 \cdot 15 $$ $$ P = 90 $$