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.
[157.698, -83.507, 141.402, 225.13, 185.354, 235.428, -7.038]