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: [-18.718, -36.75, 183.634, -16.734, 37.792, -30.623, 232.558, -78.37, 204.322]

53.012