A rectangle has a length of 7 cm and a width of 6 cm, what is the perimeter in cm?
一个长方形，长是7厘米，宽是6厘米，周长是多少厘米．
<gadget id="calculator">7 + 6</gadget>
<output>13</output>

<gadget id="calculator">13 * 2</gadget>
<output>26</output>

<result>26</result>