The perimeter of a rectangular playground is 82 meters, its length is 30 meters, and its width is in meters.
一个长方形操场的周长是82米，他的长是30米，宽是多少米．
<gadget id="calculator">82 / 2</gadget>
<output>41</output>

<gadget id="calculator">41 - 30</gadget>
<output>11</output>

<result>11</result>