What is the perimeter of a rectangle with a length of 8 decimeters and a width of 5 decimeters?
长8分米，宽5分米的长方形，它的周长是多少．
<gadget id="calculator">8 + 5</gadget>
<output>13</output>

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

<result>26</result>