A rectangle is formed with 20 cm long iron wire. If the length is 7 cm, what is the width in cm?
用20厘米长的铁丝围成一个长方形，如果长是7cm，那么宽是多少cm．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 - 7</gadget>
<output>3</output>

<result>3</result>