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.
[186.717, 123.333, 169.052, -71.105, -87.187, 18.713, -8.019, 190.853, -69.826]