The party is at my house为什么用at

The party is at my house为什么用at Mr.Johnson is the host the party is at his house. you can have your party at my house(对at my house提问） ___________to come to a party at my house this saturday? They held the party at their house in the gardon. sam is having a party at his house(提问）（）sam（）at his house? there is a party at mr jones"s house on( how about the party ( ) at john's house My name is Millie.My dream home is a big house at the top of at my house or ? That new house is ( ) at the moment I have a birthday party at my house.对have a birthday party提问