A bookbinding group needs to bind 2640 books, 240 books were bound in 3 hours. According to this calculation, how many hours will it take for the rest of the books to be bound?
一个装订小组要装订2640本书，3小时装订了240本．照这样计算，剩下的书还需要多少小时能装订完？
<gadget id="calculator">2_640 - 240</gadget>
<output>2_400</output>

<gadget id="calculator">240 / 3</gadget>
<output>80</output>

<gadget id="calculator">2_400 / 80</gadget>
<output>30</output>

<result>30</result>