There are three types of books in the school library: story books, science books, and literature and art books. The story books are the sum of science and art books (1/3). The number of science and technology books is the same as the total number of story books and literature and art books. It is known that There are 420 science books, but how many story books are there?
学校图书室有故事书、科技书、文艺书3类图书，其中故事书是科技书和文艺书和的(1/3)，科技书的本数与故事书、文艺书的总数一样多，已知科技书有420本，故事书有多少本？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">420 / (1/2)</gadget>
<output>840</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">840 * (1/4)</gadget>
<output>210</output>

<result>210</result>