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: [203.759, 212.837, -91.708, 52.778, 114.595, 52.16, 240.988, 129.009, 135.674]

116.677