The perimeter of a rectangle is 28 cm, the length is 9 cm, and the width is in cm.
一个长方形的周长是28厘米，长是9厘米，宽是多少厘米．
<gadget id="calculator">28 / 2</gadget>
<output>14</output>

<gadget id="calculator">14 - 9</gadget>
<output>5</output>

<result>5</result>