A rectangular vegetable field is 20 meters long and 8 meters wide. If there is a fence around it, how many meters should it surround?
一块长方形菜地，长是20米，宽是8米，如果四周围上篱笆，要围多少米．
<gadget id="calculator">20 + 8</gadget>
<output>28</output>

<gadget id="calculator">28 * 2</gadget>
<output>56</output>

<result>56</result>