STEP 1: find base area $ B $
To find base area $ B $ use formula:
$$ B = a^2 $$After substituting $ a = 6 $ we have:
$$ B = 6^2 $$ $$ B = 36 $$STEP 2: find lateral surface $ L $
To find lateral surface $ L $ use formula:
$$ L = 2 \cdot a \cdot s $$After substituting $ a = 6 $ and $ s = 9 $ we have:
$$ L = 12 \cdot 9 $$$$ L = 108 $$STEP 3: find total surface $ A $
To find total surface $ A $ use formula:
$$ A = B + L $$After substituting $ B = 36 $ and $ L = 108 $ we have:
$$ A = 36 + 108 $$ $$ A = 36 + 108 $$ $$ A = 144 $$