A square vegetable garden is surrounded by a fence, and the fence is 72 meters long. What is the area of the vegetable garden?
一块正方形菜园四周围了一圈篱笆，篱笆长72米，这个菜园的面积是多少？
<gadget id="calculator">72 / 4</gadget>
<output>18</output>

<gadget id="calculator">18 * 18</gadget>
<output>324</output>

<result>324</result>