The number of people in a class is 5 / 6 of that in twelve classes. The number of people in two classes is a fraction of that in one class, and the number of people in one class accounts for a fraction of the total number of people in two classes

The number of people in a class is 5 / 6 of that in twelve classes. The number of people in two classes is a fraction of that in one class, and the number of people in one class accounts for a fraction of the total number of people in two classes

6 △ 5 = 1 and 1 / 5, the number of the second class is 1 and 1 / 5 of the first class;
5 ÷ (5 + 6) = 5 / 11, the number of one class accounts for 5 / 11 of the total number of two classes