If a rectangle has a length of 10 cm and a width of 8 cm, what is the perimeter of the rectangle in cm?
一个长方形它的长是10厘米，宽是8厘米，那么这个长方形的周长是多少厘米．
<gadget id="calculator">10 + 8</gadget>
<output>18</output>

<gadget id="calculator">18 * 2</gadget>
<output>36</output>

<result>36</result>