The school bought a batch of books. Among them, there are 215 story books, and 27 science books are 3 times less than the story books. How many science books are purchased by the library?
学校购进一批书．其中故事书215本，科技书比故事书的3倍少27本，图书馆购进科技书多少本？
<gadget id="calculator">215 * 3</gadget>
<output>645</output>

<gadget id="calculator">645 - 27</gadget>
<output>618</output>

<result>618</result>