The delete option will only appear on subject areas which are not being used in any tasks.
The # Tasks column will list the number of tasks that are using the subject area. These subject areas must be removed from the tasks before it can be deleted.
Once the subject area has been removed from all of the tasks using it, the delete icon will appear. Click on the corresponding delete icon ( X ) to delete the subject area.
A confirmation box will appear, click OK to delete the subject area.