A vegetable field is an isosceles trapezoid, its upper base is 12 meters long, its lower base is 16 meters long, and its waist is 7 meters long. If a fence is built around the vegetable field, how long is the fence?
一块菜地是一个等腰梯形，它的上底长12米，下底长16米，腰长7米．如果在菜地四周围上篱笆，篱笆长多少米？
<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">12 + 16 + 14</gadget>
<output>42</output>

<result>42</result>