How can teachers delete past tasks?

Question:

A lot of past tasks have accumulated. I want to know how to delete the ones that are no longer needed.

Answer:

Tap the "Edit" button at the top right-hand of the list of tasks.
Tap the red minus button next to the task(s) you want to delete and then the "Delete" button.
Tasks that are currently waiting for answers cannot be deleted.

(Note) Please be aware the task deleted cannot be recovered.