There is a rectangular vegetable field, 7 meters long and 2 meters wide. How many meters should the fence be built around the vegetable field?
有一块长方形菜地，长7米，宽2米．要在菜地四周围上篱笆，篱笆长多少米？
<gadget id="calculator">7 + 2</gadget>
<output>9</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<result>18</result>