The school bought a batch of books and put them on two bookshelves. The number of books on the first shelf accounts for 58% of the total. If 12 books are taken from the first shelf and placed on the second shelf, then the books on the two shelves each account for 50% of the total. How many books are there in this batch?
学校买回一批图书，放在两个书架上．第一个书架放的本数占总数的58%，如果从第一个书架上取出12本放在第二个书架上，这时两个书架上的书各占总数的50%．这批图书有多少本？
<gadget id="calculator">58 / 100</gadget>
<output>29/50 = around 0.58</output>

<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(29/50) - (1/2)</gadget>
<output>2/25 = around 0.08</output>

<gadget id="calculator">12 / (2/25)</gadget>
<output>150</output>

<result>150</result>