There are two bookshelves, A and B. The number of books stored in A bookshelf is 90% of that of B bookshelf. If there are 45 books in A bookshelf, how many books are there in B bookshelf?
甲、乙两书架，甲书架存书本数是乙书架的90%，如果甲书架有45本书，那么乙书架有多少本书？
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">45 / (9/10)</gadget>
<output>50</output>

<result>50</result>