A rubber band is stretched to the limit, the ratio of the length to the original length at this time is 9:5, the length of the rubber band when it is stretched to the limit is 24 cm longer than the original length, how many centimeters is the original length of the rubber band.
把一种皮筋拉长到极限，这时的长度与原长度的比是9：5，皮筋被拉到极限时的长度比原来长了24厘米，原来皮筋长多少厘米．
<gadget id="calculator">9 - 5</gadget>
<output>4</output>

<gadget id="calculator">24 / 4</gadget>
<output>6</output>

<gadget id="calculator">6 * 5</gadget>
<output>30</output>

<result>30</result>