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: [-7.656, 27.113, -46.094, -88.382, 148.986, -55.66, 133.332, -5.579, 54.5]

17.84