Xuequan bought back a batch of books and put them on two bookshelves. The number of books placed on the first shelf accounts for (4/7) 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 half of the total. How many books are there in this batch?
学权买回一批图书，放在两个书架上．第一个书架放的本数占总数的(4/7)．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一半．这批图书有多少本？
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

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

<gadget id="calculator">(4/7) - (1/2)</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">12 / (1/14)</gadget>
<output>168</output>

<result>168</result>