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: [152.42, -48.983, 32.999, 147.185, -58.145, 65.985, 15.968, -53.935, -82.639]

18.984