The bookstore brought in 740 books, sold some, and left 180 books. How many copies did you sell? (List the equations containing the unknown x, and then answer)
书店运进740本书，卖了一些，还剩180本．卖了多少本？(列出含有未知数x的等式，再解答)
<gadget id="calculator">740 - 180</gadget>
<output>560</output>

<result>560</result>