Xiao Ming bought a schoolbag for 45 yuan and a pencil case for 15 yuan. If you pay the salesperson 100 yuan, how much should you get back?
小明买了一个45元的书包，又买了一个15元的文具盒．付给售货员100元，应找回多少元？
<gadget id="calculator">45 + 15</gadget>
<output>60</output>

<gadget id="calculator">100 - 60</gadget>
<output>40</output>

<result>40</result>