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