Exercise 1 solution

Two cells near the middle of the comb: supersedure (one or two cells, most often in the centre of the face), i.e. replacing the queen without swarming.
Fifteen cells around the edges and bottom: swarm preparation (twelve or more, often at the sides and bottom).

The article does not classify counts from 3 to 11. It matters because a real hive may show such a number, and then the count alone cannot tell you which process is under way.