STEP 1: find base area $ B $
To find base area $ B $ use formula:
$$ B = a^2 $$After substituting $ a = 8 $ we have:
$$ B = 8^2 $$ $$ B = 64 $$STEP 2: find lateral surface $ L $
To find lateral surface $ L $ use formula:
$$ L = 2 \cdot a \cdot s $$After substituting $ a = 8 $ and $ s = 12 $ we have:
$$ L = 16 \cdot 12 $$$$ L = 192 $$STEP 3: find total surface $ A $
To find total surface $ A $ use formula:
$$ A = B + L $$After substituting $ B = 64 $ and $ L = 192 $ we have:
$$ A = 64 + 192 $$ $$ A = 64 + 192 $$ $$ A = 256 $$