The length of a rectangle is 7 cm, the circumference is 24 cm, and the width is in cm.
一个长方形的长是7厘米，周长是24厘米，宽是多少厘米．
<gadget id="calculator">24 / 2</gadget>
<output>12</output>

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

<result>5</result>