## Elementary Statistics (12th Edition)

This is only 1 out of the ${5 \choose 2}$ possiblities.
We want to know the probability of exactly two adults including Wal-Mart. In the construction, we are given that the first two adults include Wal-Mart, and the other 3 don't. However, this is only 1 out of the ${5 \choose 2}$ possiblities, and we have to count those too.