The mean is the average. To find it, you add all of the numbers together.
2 + 8.7 + 11.9 + 3.3 + 4.2 + 2.2 + 13.4 = 45.7
Now you divide the total by the amount of numbers you added. Because you added 7 numbers, you divide 45.7 by 7.
45.7 ÷ 7 = 6.52 (This is the mean.)
To find the median you have to put all of the numbers in order of least to greatest.
2 2.2 3.3 4.2 8.7 11.9 13.4
The median is the number in the very middle. In this case, it is 4.2.