Report showing Opportunities that have no associated Tasks

Content

For context, our structure for this work type is:

Incident joined to Opportunity

The Opportunity then may or may not have a task. If there *is* a task, then they would all have the same "Task Name".

 

It's probably obvious (my head is mashed!) - but I'm trying to run a report that shows all Opportunities with no associated task.

 

Could someone please explain how to do this? What filters should I use? What table joins?

 

TIA!

 

Version

18b