With her mom and dad. In sentences like that, the subject is always understood as the possessor of the object. Other examples (bold parts are only implied);
Я живу с мамой и папой - I live with my mom and dad
Ты жвёшь с мамой и папой - You live with your mom and dad
Он живёт с мамой и папой - He lives with his mom and dad
That's a heck of a question!
From an English speaker's (US) standpoint I would also think it's the speaker's mom and dad, not necessarily the girl's mom and dad (though they could be the same - but that's not at all clear here, either).
Now following this thread hoping someone answers.
As an English speaker hearing this sentence spoken aloud, the lack of any determiner* implies a proper noun, so "The girl lives with Mom and Dad"; this is still a bit ambiguous but typically proper nouns for family members are only used relative to the speaker. I cannot imagine how subtle this kind of thing would be for a native Russian speaker, but we have to return the favor for the perfective/imperfective verb thing somehow ;)
*Theoretically including "the", "a(n)", etc, but here almost always a possessive. Theoretical linguists would say this phrase features a "zero article", but that's not much help to a learner.
Thanks for that clarification, Theron126. However, no doubt due to the extreme thickness of my skull, enlightenment still eludes me. First, how do I know if a word with a feminine ending is in fact of the masculine gender? Second, is it only in the case of words whose substance is clearly masculine? And Third, are all masculine words with feminine endings declined as “feminine” words? And I do hope that your answer will not be that there is no rule, that I must just memorize those words. This geezer’s grey matter, already settled into senescence and heading for senility, does not need another such burden. Your heroic efforts to shine a glimmer of light into my tenebrous cranium are much appreciated. Спасибо, друг мой.
This situation used to confuse me, due to its being referred to as a "feminine ending". It is perhaps better to say simply that it is a "first declension noun". First declension nouns end in -а, -я or -ия in the nominative singular, and it happens that the majority of these are feminine. Having established that they are 1st declension, the endings in other cases are fixed by that - the actual gender is irrelevant.
But adjectives agree with number, case and gender, regardless of the declension of the noun to which they are applied. So you can get a situation where the adjective ending is different to that of the noun to which it is applied.
The majority of masculine nouns in the 1st declension seem to be either obviously masculine (e.g. дедушка - grandfather), diminutives of masculine nouns - in particular the familiar forms of most Russian names - or words describing male professions.
Eureka! Kudos to you, Daughter of Albion, for your Promethean accomplishment. In the words of the old hymn, “I was lost, but now I’m found; was blind, but now I see.” Joy is mine! So, I’m to treat all second declension nouns the same, regardless of their gender; that is, decline them all as feminine nouns. Simple enough. Thanks, again. After a bit of reflection, though, I find my joy somewhat diminished. As in much of life, the successful vanquishing of one obstacle, simply leads to the next. In the matter at hand, after declining a noun via the aforementioned simple rubric, I must deal with its attendant adjectives. And that, if I understand correctly, requires that I first determine the gender of the aforementioned noun, because that determines how I decline those adjectives. I’m back where I started. What sadistic S.O.B.devised this crazy-making concoction? Come to think of it, though, our own native tongue “ain’t no picnic, neither,” is it? On a more positive note, I’ve heard it said that scientific studies have shown that the exercise of mental gymnastics--like wrestling with the Russian language at an advanced age--will likely deter or at least slow the development of Alzheimer’s disease. Ещё раз, спасибо!
Be of good cheer, my friend! Russian is much kinder than either French or German in the matter of gender of nouns. The apparently random association of masculine or feminine qualities to inanimate objects is hard on us - particularly when these languages do not agree on the same (French tables are feminine, whilst Russian and German tables are masculine).
But Russian is our friend - it takes the gender from the ending of the noun, with very few exceptions.
And on the subject of these pesky exceptions, please reread my 3rd paragraph. The male nouns of this declension (i.e. ending in -а, -я, etc.) are all such as are what one could call " naturally masculine" i.e. they are male by their meaning, not by some arbitrary rule of grammar.
There are so many sentences which do not accept an indefinite article even though it is obviously correct. Rather than keep reporting it and waiting months/years (it was reported more than a year ago) until the moderators correct a single sentence, I'd kindly like to ask the moderators to go through all the sentences at once and correct them all. It will be a big help for duolingo and all the community here. If there is any way I can help with it, please let me know!