The length of the rectangular iron sheet is 24 cm. After the four corners are cut off to make a square with a side length of 3 cm, it is then welded into a rectangular box. The volume of the box is 486 cubic centimeters. Find the width of the original rectangular iron sheet.
长方形铁皮长24厘米，四角剪去边长3厘米的正方形后，再焊接成长方体盒子，盒子容积是486立方厘米，求原长方形铁皮宽．
<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">24 - 6</gadget>
<output>18</output>

<gadget id="calculator">3 * 18</gadget>
<output>54</output>

<gadget id="calculator">486 / 54</gadget>
<output>9</output>

<gadget id="calculator">9 + 6</gadget>
<output>15</output>

<result>15</result>