What is the perimeter of a rectangle whose width is 3 cm and length is 5 cm?
一个长方形的宽是3厘米，长是5厘米，它的周长是多少．
<gadget id="calculator">3 + 5</gadget>
<output>8</output>

<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<result>16</result>