To find area $ A $ use formula:
$$ A = \frac{ a^2 \sqrt{3}}{2} + 3 a l $$After substituting $ a = 8 $ and $ l = 24 $ we have:
$$ A = \frac{ 8^2 \sqrt{3}}{2} + 3 \cdot 8 \cdot 24 $$$$ A = \frac{ 64 \sqrt{3}}{2} + 3 \cdot 192 $$$$ A = \frac{ 64 \sqrt{ 3 }}{2} + 576 $$$$ A = 32 \sqrt{ 3 } + 576 $$$$ A = 631.4256 $$