The school library brings in a batch of new books. If every 120 books are packed into a pack, the difference of 20 books can be packed into 5 packs. How many new books are there in total?
学校图书馆运进一批新书，如果每120本包成一包，差20本可以包成5包．这批新书一共有多少本？
<gadget id="calculator">120 * 5</gadget>
<output>600</output>

<gadget id="calculator">600 - 20</gadget>
<output>580</output>

<result>580</result>