literally: ma maison a douze pièces, more naturally: il y a douze pièces dans ma maison.
ma maison a trois (3) pieces.
ce sont les pièces de la maison
'twelve' in french is 'douze'
'une arrière-cuisine' or 'un cellier' are the rooms were you store food and kitchen items in a house.
sept pièces
Elle a douze ans.
'le vestiaire' (most often used in the plural: les vestaires) is the name for the locker rooms in French.
j'ai douze ans
twenty-twelve (2012) is "deux-mille-douze" in french. I'm trying to figure out whether you can say "vingt-douze", which would be the literal translation of twenty-twelve, but it seems this is not something that translates directly.
The house is "la maison" (fem.) in French.
To say "the house of" in French, you would say "la maison de."
J'ai douze ans.