The perimeter of a rectangle is 54 cm, its length is 18 cm, and its width is in cm.
一个长方形的周长是54厘米，它的长18厘米，宽是多少厘米．
<gadget id="calculator">54 / 2</gadget>
<output>27</output>

<gadget id="calculator">27 - 18</gadget>
<output>9</output>

<result>9</result>