A rectangle has a length of 9 cm and a width of 6 cm. When the length is shortened by a certain number of cm, the rectangle becomes a square.
一个长方形长9厘米，宽6厘米，把长缩短多少厘米后，长方形就变成正方形．
<gadget id="calculator">9 - 6</gadget>
<output>3</output>

<result>3</result>