There are two bookshelves, A bookshelf has 80 books, and B bookshelf has 50 books. Each time, take 3 books from A bookshelf and put them in B bookshelf. How many times are the books on the two bookshelves equal.
有两个书架，甲书架有书80本，乙书架有书50本，每次从甲书架拿出3本放入乙书架，拿多少次后两个书架的书相等．
<gadget id="calculator">80 - 50</gadget>
<output>30</output>

<gadget id="calculator">30 / 2 / 3</gadget>
<output>5</output>

<result>5</result>