A square vegetable field is surrounded by a wall on one side and fences on the other three sides. The length of the fence is 27 meters. What is the area of this vegetable field in square meters?
一块正方形菜地，一面靠墙，其他三面围篱芭，篱笆长是27米，这块菜地的面积是多少平方米．
<gadget id="calculator">27 / 3</gadget>
<output>9</output>

<gadget id="calculator">9 * 9</gadget>
<output>81</output>

<result>81</result>