Obviously there are some books, among which (2/5) is 10 books donated, how many books are there?
明明有一些图书，捐了其中的(2/5)是10本，明明有多少本图书．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">10 / (2/5)</gadget>
<output>25</output>

<result>25</result>