What is the average age of the students in a class if the ages of 30 students are 12, 13, 14, 11, 12, 13, 15, 12, 11, 13, 14, 12, 13, 14, 11, 12, 13, 15, 12, 11, 13, 14, 12, 13, 14, 11, 12, 13, 15, and 12?
+
What is the number of ways to arrange 7 books on a shelf if 2 specific books must be next to each other?