The length of a rectangle is 8 meters and the width is 4 meters. What is the perimeter of the rectangle?
一个长方形的长是8米，宽是4米，这个长方形的周长是多少米．
<gadget id="calculator">8 + 4</gadget>
<output>12</output>

<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<result>24</result>