The perimeter of a rectangle is 24 cm, its length is 7 cm, and its width is in cm.
长方形周长是24厘米，长7厘米，宽多少厘米．
<gadget id="calculator">24 / 2</gadget>
<output>12</output>

<gadget id="calculator">12 - 7</gadget>
<output>5</output>

<result>5</result>