Mean absolute deviation of 75, 89, 145, 85, 80, 92, 104, 90, 100?

First, compute the mean:

Next compute the absolute deviations for each datapoint:
|75-95.555|=20.555
|89-95.555|=6.555
|145-95.555|=49.445
|85-95.555|=10.555
|80-95.555|=15.555
|92-95.555|=3.555
|104-95.555|=8.445
|90-95.555|=5.555
|100-95.555|=4.445

Next we'll take the mean of these deviations:

The mean absolute deviation of your data is 13.8517

The answer is all about the number 4