There are two bookshelves. The books on shelf A are less than those on shelf B (1/5). Now take 40 books from shelf B and put them on shelf A. The books on shelf B are 60 fewer than the books on shelf A. How many books are there on the B bookshelf?
有两个书架，甲书架的书比乙书架的书少(1/5)，现从乙书架取出40本放到甲书架上，乙书架上的书就比甲书架上的书少60本，乙书架原有多少本书．
<gadget id="calculator">40 - 60</gadget>
<output>-20</output>

<gadget id="calculator">40 + (-20)</gadget>
<output>20</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) - 1</gadget>
<output>-4/5 = around -0.8</output>

<gadget id="calculator">1 + (-4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">20 / (1/5)</gadget>
<output>100</output>

<result>100</result>