The school bought some exercise books and distributed them to 15 classes. Each class had 164 books, and there were 420 books left. How many copies did you buy in total?
学校买来一些练习本，分给15个班，每班164本，还剩420本．一共买几本？
<gadget id="calculator">164 * 15</gadget>
<output>2_460</output>

<gadget id="calculator">2_460 + 420</gadget>
<output>2_880</output>

<result>2_880</result>