Answer:
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 :