The library of the foreign language primary school originally had 15,000 sets of books, and after some of them were lent out, another 2,000 sets were brought in. The library now has 9,000 sets of books. How many sets have you lent out?
外国语小学图书馆原有图书15000套，借出一些后，又进了2000套，图书馆这时有图书9000套．借出了多少套？
<gadget id="calculator">9_000 - 2_000</gadget>
<output>7_000</output>

<gadget id="calculator">15_000 - 7_000</gadget>
<output>8_000</output>

<result>8_000</result>