Given only the first piece of information, the options (a<=b<=c) are:
1,3,12 -> 16
1,6,6 -> 13
2,2,9 -> 13
2,3,6 -> 11
3,3,4 -> 10
The guest will obviously know the house number, so not knowing the answer at this stage tells us it must be 13.
The second clue tells us that of the 2 options, it is the latter.
This isn't our regular choice of puzzle type here. However, I think some people enjoy this type of puzzle nevertheless.
Please take the time to explore the world of logic puzzles, as referenced universally in these forums.