Two wires of equal length, one enclosing a rectangle and the other enclosing a square. The side length of the square is 9 cm, the length of the rectangle is 12 cm, and the width in cm.
两根一样长的铁丝，一个围成长方形，一个围成正方形．正方形边长是9厘米，长方形长12厘米，宽多少厘米．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<gadget id="calculator">18 - 12</gadget>
<output>6</output>

<result>6</result>