There are 42 rolls in the cafeteria.
how can they be divided into 2 groups so that they are in a ratio of 2: 5. how many rolls will be in each group?

42 can be divided by 7 to be 6, right?
That means you have 7 groups of 6 rolls each.
So, if you want to separate those rolls into 2 groups for a 2:5 ratio, (note: 2:5 is 7 groupings total), then you'd put 12 rolls into one group and 30 in the other group.

You would have atleast 21 rolls in each gruop.

He was paid 23 dollars for each lawn