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.
[-45.751, 19.247, 171.55, 107.313, 145.286, 150.336, 46.239]