A rectangular vegetable field is 18 meters long and 10 meters wide, one side is against a wall, and the other three walls are surrounded by bamboo fences. How long is the bamboo fence?
一块长方形菜地，长18米，宽10米，一面靠墙，其它三面墙围上竹篱笆．竹篱笆长多少米？
<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">18 + 20</gadget>
<output>38</output>

<result>38</result>