Xiao Ming bought a set of "Stories of Mathematicians" series. There are 6 books in this series, and each book is 12 yuan. I gave the salesperson 100 yuan, how much should I get back?
小明买了一套《数学家的故事》丛书，这套丛书有6本，每本12元．给了售货员100元，应找回多少元？
<gadget id="calculator">12 * 6</gadget>
<output>72</output>

<gadget id="calculator">100 - 72</gadget>
<output>28</output>

<result>28</result>