Translation:What is your favorite subject at school?
RU: Kakoj jest' twoj liubimyj priedmiet w szkolie?
UA: Jakyj je twij uliublennyj predmet u szkoli?
CZ: "Jaký je váš oblíbený předmět ve škole"
HR: "Koji je Vaš omiljeni predmet u školi"
SK: "Aký je váš obľúbený predmet v škole"
SLO: "Kaj je vaš najljubši predmet v šoli"
Spelled in Polish for those who don't read Cyrillic:
MK: Szto e wasiot omilen predmet wo uciliszte?
BG: Koja e liubimata ti predmet w uciliszte?
BY: Jaki joscj' twoj liubimy pradmiet u szkolie?
In RU you would say: Какой у тебя любимый предмет в школе? (Kakoj u tebia liubimyj priedmiet w szkolie?)
Thank you for writing the Russian in Cyrillic. People are always writing it in Latin on these pages and it makes it much harder to read.
Oh, it's a difficult question, I guess :) It has historical roots, which noun requires which preposition. You can infer some general rules for particular cases but practically, you have to memorize the correct combination for each word.
'u' is basically used for 'at someone's place'.
Jestem u babci = I'm at grandma's (place/house/apartment}.
True, but unfortunately you often cannot rely on this. So, for ex., you have to say "na dworcu", "na poczcie", "na ulicy", whereby you mean 'inside'
"What is your favorite object at school?" I guess it's technically correct although in 99% of the cases it's asking the subject.