If the length of a rectangle is 6 meters and its width is 3 meters, what is its perimeter?
一个长方形的长是6米，比宽多3米，它的周长是多少．
<gadget id="calculator">6 - 3</gadget>
<output>3</output>

<gadget id="calculator">6 + 3</gadget>
<output>9</output>

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

<result>18</result>