Mr. Zhang went to buy books. He bought a science book worth 18.7 yuan and a dictionary worth 15.3 yuan. He paid the salesperson 100 yuan. How much should he get back?
张老师去买书，买了18.7元的科技书一本，又买了15.3元的字典，它付给营业员100元，应找回多少元？
<gadget id="calculator">100 - 18.7 - 15.3</gadget>
<output>66</output>

<result>66</result>