A rectangular wire circle is 7 cm long, and 18 cm long wire is used to enclose this wire circle. What is the width of this wire circle in centimeters?
一个长方形的铁丝圈，长是7厘米，围成这个铁丝圈刚好用了18厘米长的铁丝，这个铁丝圈的宽是多少厘米？
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">9 - 7</gadget>
<output>2</output>

<result>2</result>