There are 300 story books in the school library, and the number of science books is 40 less than twice the number of story books. How many textbooks are there?
学校图书室有故事书300本，科技书的本数比故事书的2倍少40本，科科书有多少本？
<gadget id="calculator">300 * 2</gadget>
<output>600</output>

<gadget id="calculator">600 - 40</gadget>
<output>560</output>

<result>560</result>