To find area $ A $ use formula:
$$ A = \frac{ a^2 \sqrt{3}}{2} + 3 a l $$After substituting $ a = 12 $ and $ l = 17 $ we have:
$$ A = \frac{ 12^2 \sqrt{3}}{2} + 3 \cdot 12 \cdot 17 $$$$ A = \frac{ 144 \sqrt{3}}{2} + 3 \cdot 204 $$$$ A = \frac{ 144 \sqrt{ 3 }}{2} + 612 $$$$ A = 72 \sqrt{ 3 } + 612 $$$$ A = 736.7077 $$