A rectangle is 3 meters wide and twice as long as it is wide, what is the perimeter of the rectangle?
一个长方形宽3米，长是宽的2倍，这个长方形的周长是多少．
<gadget id="calculator">3 * 2</gadget>
<output>6</output>

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

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

<result>18</result>