The supermarket bundles 5 big bags of milk and 1 small bag of milk together for sale (buy 5 big bags and get 1 small bag free), now there are 60 big bags and 20 small bags of milk, after how many bundles are tied, the remaining big bags of milk and small bags of milk are equal?
超市将5大袋牛奶和1小袋牛奶捆在一起出售(买5大赠1小)，现在有60大袋和20小袋牛奶，问捆多少捆后，剩下的大袋牛奶和小袋牛奶的袋数相等？
<gadget id="calculator">60 - 20</gadget>
<output>40</output>

<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">40 / 4</gadget>
<output>10</output>

<result>10</result>