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.
[165.475, 0.169, 157.921, 103.792, -20.858, -20.668, 60.146]