The length of a rectangle is 20 meters and twice its width, what is the perimeter of the rectangle in meters?
长方形长是20米，是宽的2倍，这个长方形的周长是多少米．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<gadget id="calculator">30 * 2</gadget>
<output>60</output>

<result>60</result>