Teacher Wang bought four books, including three "Fairy Tale World" and one "Mathematics Handbook". ． Teacher Wang gave the salesperson 100 yuan, how much should I get back?
王老师买了四本书，其中买了三本《童话世界》和一本《数学手册》，每本《童话世界》12.3元，每本《数学手册》比每本《童话世界》贵4.2元．王老师给了售货员100元，应找回多少元？
<gadget id="calculator">12.3 * 3</gadget>
<output>36.9</output>

<gadget id="calculator">12.3 + 4.2</gadget>
<output>16.5</output>

<gadget id="calculator">100 - 36.9 - 16.5</gadget>
<output>46.6</output>

<result>46.6</result>