If a rectangle is 7 cm wide and twice as long as it is wide, what is the perimeter in cm?
一个长方形宽7厘米，长是宽的2倍，周长是多少厘米．
<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">14 + 7</gadget>
<output>21</output>

<gadget id="calculator">21 * 2</gadget>
<output>42</output>

<result>42</result>