A rectangular vegetable field is 6 meters long and 3 meters wide. A fence is built around it. How long is the fence?
一块长方形菜地，长6米，宽3米．四周围上篱笆，篱笆长多少米？
<gadget id="calculator">6 + 3</gadget>
<output>9</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<result>18</result>