Teacher Wang spent 36 yuan to buy a USB flash drive and 85 yuan to buy 5 CDs. How much is a CD cheaper than a USB?
王老师买一只优盘用去36元，买5只光盘用去85元．一张光盘比一只优盘便宜多少元？
<gadget id="calculator">85 / 5</gadget>
<output>17</output>

<gadget id="calculator">36 - 17</gadget>
<output>19</output>

<result>19</result>