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: [20.796, 39.383, -26.46, -27.224, 89.591, 87.502, 211.781, 127.87, 223.38]

82.958