The perimeter of a rectangle is 20 cm, the length is 8 cm, and the width is in cm.
一个长方形的周长是20厘米，长是8厘米，宽是多少厘米．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 - 8</gadget>
<output>2</output>

<result>2</result>