Xiaojun bought a schoolbag for 65 yuan and a stationery box for 15 yuan. He gave the salesperson 100 yuan. How much should he get back?
小军买一个书包65元，买一个文具盒15元，他给售货员100元，应找回多少钱？
<gadget id="calculator">65 + 15</gadget>
<output>80</output>

<gadget id="calculator">100 - 80</gadget>
<output>20</output>

<result>20</result>