Teacher Wang took 200 yuan to buy prizes for the students. Each notebook is 8 yuan. If you want to buy 15 copies, how much should you get back?
王老师拿了200元钱为学生买奖品，笔记本每本8元，要买15本，应找回多少元．
<gadget id="calculator">15 * 8</gadget>
<output>120</output>

<gadget id="calculator">200 - 120</gadget>
<output>80</output>

<result>80</result>