In this task you will be given a list of numbers and you need to find the mean (average) of that list. The mean of a list can be found by summing every number in the list then dividing the result by the size of that list. The output should be rounded to 3 decimal places.

[-7.775, 55.997, 216.046]
88.089

[74.601, 131.018, -45.91]
53.236

[-67.391, 16.577, 154.11]

34.432