Had it exactly as shown and was marked incorrect
You'll have to submit a report, there's nothing we can do if we can't see what answer you put :)
How do you tell the difference between when you use the formal/informal when all you have is names? Titles I understand, but just names?
The formal singular is the same as the plural. So given that you are addressing two people here, you have to use "mealaibh ur..." and not "meal do..." :)