A rectangular flowerbed is 12 meters long and 9 meters wide. One side of it is against the wall, and the other three sides are surrounded by fences. How long is the fence at least?
一块长方形花圃，长12米，宽9米，它的一条边靠墙，其余三条边围上篱笆．篱笆至少要多少米？
<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<gadget id="calculator">12 + 18</gadget>
<output>30</output>

<result>30</result>