Final answer:
You can add a Delete lock to an Azure resource even if it has a Read-only lock; the Read-only lock prevents changes to the resource's state, while a Delete lock prevents accidental deletion.
Step-by-step explanation:
If an Azure resource has a Read-only lock, it is still possible to add a Delete lock to the resource. The purpose of the Read-only lock is to prevent users from making changes to the resource that would alter its state. However, adding a Delete lock is not considered a change to the resource's state, but rather an addition to the resource's policy settings. Therefore, you can indeed apply a Delete lock on a resource that already has a Read-only lock, providing a combination of protection against both modifications and accidental deletion.