The school spent 180 yuan to buy 9 CDs, which is the same as buying 30 floppy disks. How much is a floppy disk cheaper than a CD?
学校买9张光盘用去180元，和买30张软盘的价钱一样多．一张软盘比一张光盘便宜多少元？
<gadget id="calculator">180 / 9</gadget>
<output>20</output>

<gadget id="calculator">180 / 30</gadget>
<output>6</output>

<gadget id="calculator">20 - 6</gadget>
<output>14</output>

<result>14</result>