The length of a rectangular vegetable field is 20 meters, and the width is 4 meters less than the length. A fence is to be built around the rectangular vegetable field. What is the length of the fence?
一块长方形菜地的长是20米，宽比长少4米，要在长方形菜地的四周围上篱笆，篱笆长多少米．
<gadget id="calculator">20 - 4</gadget>
<output>16</output>

<gadget id="calculator">20 + 16</gadget>
<output>36</output>

<gadget id="calculator">36 * 2</gadget>
<output>72</output>

<result>72</result>