If the adjacent sides of a parallelogram are 9 cm and 7 cm long, what is its perimeter?
平行四边形相邻两边长分别是9厘米和7厘米，它的周长是多少．
<gadget id="calculator">9 + 7</gadget>
<output>16</output>

<gadget id="calculator">16 * 2</gadget>
<output>32</output>

<result>32</result>