A number of people do a job together, and 5 people do not participate because of work needs, so the remaining people have to work for 1 day each, and when the work starts, 8 people quit, so the remaining people work for 2 more days ． How many days did each person do it?
若干人共同做一项工作，后来有5人因工作需要不参加，这样余下的人就得每人各做1天，临开工时，又有8人退出，于是最后余下的人又多做2天．问原来每人做多少天？
<result>12</result>