My math teacher is giving me a question about the mean absolute deviation. i don't really get it. some .

Well, you didn't show the question but i can tell you this: first find the mean of the data set.
1) 1+2+3+4=10    10/4(amount of #)=2.5
then, subtract the mean from each number in the data set.
2) 1-2.5= -1.5; 2-2.5= -0.5; 3-2.5= 0.5; 4-2.5= 1.5
convert all these numbers to positive, then add them together.
3)1.5 + 0.5 + 0.5 +1.5 = 4
divide the total by the amount of # in the data set
4/4=1
the MAD in this case is 1.

Hope i helped!! :)