"My brother is at mom's place."
Translation:Мой брат у мамы.
It would appear that is exactly how Y is being used here.
Y indicates possession. If context or the content leaves the thing possessed unspecified, the assumption is that it is someone's place
In English, if you say ...he is at Jim's ....the assumption, unless indicated otherwise, that he is at some place that is considered to be Jim's.
Could this also mean simply "My brother is with Mom" = not referring to a place, but just being near or with Mom? For example, Mom decides to visit relatives in Siberia - Papa, maybe - and a friend wants to know if she went by herself. Could you say, «Мой брат у мамы» ?
NB: Used Windows 10 Mnemonic keyboard for Russian text and Alt+0171, Alt+0187 for double-arrow bracket Russian quotation marks.
This is perfectly valid too. As a native speaker I use находится frequently.
In the sentence "Мой брат у мамы" the word находится is implicitly assumed and is skipped only for convenience.
I think that the variant without находится is a little bit more common in informal language (because it's shorter). And the variant without находится is a little bit more common in literature and official language. But in my experience both variants are used very frequently.
How am supposed to type something in Russian without a Russian keyboard? The lesson won't let me continue without completing the question...I can't 'skip' and I can't answer.I get stuck at the same places time after time after time. I am so frustrated. And when I quit the lesson all my progress is lost.