Definition: 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.
Input: [-96.182, -37.177, 130.645, -44.92, -12.78, 90.335, -99.791, -11.926, 217.275]

15.053