There are 80 books on shelf A, and 50 books on shelf B. Every time you take 5 books from shelf A and put them on shelf B, after how many times you take them, there are as many books on the two shelves.
甲书架上有80本书，乙书架上有50本书，每次从甲书架上拿出5本放到乙书架上，拿多少次后两个书架上的书一样多．
<gadget id="calculator">80 + 50</gadget>
<output>130</output>

<gadget id="calculator">130 / 2</gadget>
<output>65</output>

<gadget id="calculator">65 - 50</gadget>
<output>15</output>

<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<result>3</result>