A rectangle is 12 cm long and 5 cm wide, what is the perimeter in cm?
一个长方形，长12厘米，宽5厘米，周长是多少厘米．
<gadget id="calculator">12 + 5</gadget>
<output>17</output>

<gadget id="calculator">17 * 2</gadget>
<output>34</output>

<result>34</result>