A 28-meter-long iron wire is used to surround a square field, and the wire is just used up. What is the side length of the field in meters?
用28米长的铁丝环绕一个正方形场地一圈，铁丝正好用完，这个场地的边长是多少米？
<gadget id="calculator">28 / 4</gadget>
<output>7</output>

<result>7</result>