The perimeter of a rectangle is 24 meters, the length is 8 meters, and the width is in meters.
一个长方形的周长是24米，长是8米，宽是多少米．
<gadget id="calculator">24 / 2</gadget>
<output>12</output>

<gadget id="calculator">12 - 8</gadget>
<output>4</output>

<result>4</result>