A rectangular vegetable field is 12 meters long and 6 meters wide. One side of the vegetable field is against the wall, and the other three sides are surrounded by bamboo fences. How many meters of bamboo fences are needed at least?
一块长方形菜地，长12米，宽6米，这块菜地的一面靠墙，其它三面要围上竹篱笆，至少需要竹篱笆多少米？
<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<gadget id="calculator">12 + 12</gadget>
<output>24</output>

<result>24</result>