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: [-15.842, 203.934, 1.146, 230.272, 145.962, 67.736, 119.41, 205.691, 148.317]

122.958