There are two bookshelves, A and B. Take 15 books from A and put them in the B bookshelf. At this time, the books on the B bookshelf happen to be A’s (5/7). B has 35 books. How many books does A have?
甲乙两个书架，从甲取出15本放入乙书架，这时乙书架的书正好是甲的(5/7)，乙原有书35本，甲现有多少本？
<gadget id="calculator">35 + 15</gadget>
<output>50</output>

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

<gadget id="calculator">50 / (5/7)</gadget>
<output>70</output>

<result>70</result>