Xinhua Bookstore bought 180 bundles of new story books, each bundle of 25, and sold 825. Please ask a mathematical question and answer it.
新华书店新进180捆新故事书，每捆25本，卖出了825本．请你提出一个数学问题，并解答．
<gadget id="calculator">180 * 25</gadget>
<output>4_500</output>

<gadget id="calculator">4_500 - 825</gadget>
<output>3_675</output>

<result>3_675</result>