Each pen is 15 yuan. There are 48 people in classes 3 and 9. Each person buys a pen and gives 800 yuan to the salesperson. How much should I get back?
每只钢笔15元，三9班有48人，每人买一只钢笔，给售货员阿姨800元钱，应找回多少元？
<gadget id="calculator">15 * 48</gadget>
<output>720</output>

<gadget id="calculator">800 - 720</gadget>
<output>80</output>

<result>80</result>