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.
[-57.838, -63.616, 49.646, -45.262, 73.1, -82.399, 47.168]