Need to count field specific value in Views
You first create  a views to show the list of  open or closed task.

create a views with content type  "project" remove all field  then add a relation on task referenced field ,add title field with consider that you select relation field for it (because we want load task title instead of project title) then add  filter   "task_status" equal to close,then enable exaggeration and on title.and finally for better result you can get the title(or nid ) of project with contextual filter . it help you you can get only the list of tasks form specified  project.( and finally create another page in that views with only one change,  status=open ).