A rectangular vegetable garden is 8 meters long and 5 meters wide. A fence should be built around it. How long is the fence?
一个长方形菜园，长8米，宽5米，要在四周围上篱笆，篱笆长多少米？
<gadget id="calculator">8 + 5</gadget>
<output>13</output>

<gadget id="calculator">13 * 2</gadget>
<output>26</output>

<result>26</result>