The school bought a batch of books, including 239 science and technology books, and the number of story books is 170 less than three times that of science and technology books. How many story books are there?
学校买来一批书，其中科技书239本，故事书的册数比科技书的3倍少170本．故事书有多少本？
<gadget id="calculator">239 * 3</gadget>
<output>717</output>

<gadget id="calculator">717 - 170</gadget>
<output>547</output>

<result>547</result>