Answer :

AL2006

This is an unusual way of presenting a set of data.   Usually, when they ask for the mean, it's the mean of a bunch of numbers.  In this problem, it's the mean of some property of a bunch of points. 

Look at the points on the graph.
There are ten points:

  There are  2  points where Variable A is 1.
  There are  2  points where Variable A is 2.
  There is  1  point where Variable A is 3.
  There is  1  point where Variable A is 4.
  There are no points where Variable A is 5.
  There is  1  point where Variable A is 6. 
  There is  1  point where Variable A is 7.
  There is  1  point where Variable A is 8.
  There are no points where Variable A is 9.
and
  There is  1  point where Variable A is 10.

So there you have the ten numbers for Variable A :

                         1,  1,  2,  2,  3,  4,  6,  7,  8,  10.      

To find their mean:

                             Addum up:                44

                             Divide the sum by 10:  4.4