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

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

<result>5</result>