The absolute deviation is just the deviation in the second column, but "absolute" here means that they don't want negative values included. So your third column would look like:
10
10
10
5
5
0
5
5
15
15
b. The mad would be the average of the numbers from column 3: (10+10+10+5+5+0+5+5+15+15)/10 = 8-so the average deviation from the mean of 15 is 8.
2. The MAD of this data set tells you that most of the donations fell in the range of 15 plus or minus 8 dollars.
3. The deviation is positive if the value is greater than the mean, the deviation is negative if the value is less than the mean, and the deviation is zero if the value is the mean.
