Among them, 3 1 person is both completed, which is duplicate, and it needs to be subtracted: 79-3 1=48 people.
So the total number of people is: (37+42-3 1)=48.
(Premise: the number of students who have not finished both homework in the class is 0, and if there are n students who have not finished both homework, the total number is 48+n)