1. Find the mean that is the average value:

2. The median is the "middle" of a sorted list of numbers. For the numbers
12, 12, 12, 12, 13, 13, 15
the median is 12.
3. The mode is simply the number which appears most often. For the numbers
12, 12, 12, 12, 13, 13, 15
- the number 12 appears 4 times;
- the number 13 appears twice;
- the number 15 appears once.
Then the mode is 12.
Answer: B and C.