The school bought 1,560 exercise books, and after distributing some of them, there were 564 left. How many exercise books did the school distribute? (List the equations involving the unknown x, and then solve them)
学校买来1560个练习本，发了一部分后，还剩564本，学校发了多少个练习本？(列出含有未知数x的等式，再解答出来)
<gadget id="calculator">1_560 - 564</gadget>
<output>996</output>

<result>996</result>