There are 840 story books in the school library, which is less than science books (3/5). How many science books are there?
学校图书馆有故事书840本，比科技书少(3/5)，科技书有多少本？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">840 / (2/5)</gadget>
<output>2_100</output>

<result>2_100</result>