The perimeter of a rectangle is 34 cm, its length is 12 cm, and its width is in cm.
一个长方形的周长是34厘米，它的长是12厘米，宽是多少厘米．
<gadget id="calculator">34 / 2</gadget>
<output>17</output>

<gadget id="calculator">17 - 12</gadget>
<output>5</output>

<result>5</result>