Answer:

Explanation:
The first thing to identify is that this one is a consecutive set, meaning that the increment between each number is the same, in this case, an increment of 3 between each number, when sets have this type of behavior, and only on these cases, the mean and the median are the same, let's look at some examples:
[2, 4, 6, 8, 10, 12]
The mean would be:
mean=
=7
Since the number of elements is even, the median would be the average of the two middle terms:
median=
=7
As you can see mean=median
There is one more thing to help you in this exercise, for consecutive sets, the mean can also be calculated by the formula:

Where
is the first term of the set and
is the last.
If we ran this formula with the set i used as an example:
mean=
.
So applying all of that to the set given we would have:
