The school purchased a batch of popular science books and distributed them to three classes. Class A received 42% of the books, Class B received 5/7 books from Class A, and Class C received 2 fewer books than Class B. How many books are there in total?
学校购进一批科普书，分给三个班，甲班分到这批书的42%，乙班分到甲班的(5/7)，丙班分到的比乙班少2本，这批科普书一共有多少本？
<gadget id="calculator">42 / 100</gadget>
<output>21/50 = around 0.42</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(21/50) * (5/7)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (21/50) - (3/10)</gadget>
<output>7/25 = around 0.28</output>

<gadget id="calculator">(3/10) - (7/25)</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">2 / (1/50)</gadget>
<output>100</output>

<result>100</result>