Сімнадцять людей у кімнаті.

In Ukrainian, the present-tense verb to be is often omitted.

So Сімнадцять людей у кімнаті is literally something like Seventeen people in the room, but it naturally means There are seventeen people in the room.

You can sometimes use є for there is/there are, especially if you want to emphasize existence:

У кімнаті є сімнадцять людей.

But in many everyday sentences, leaving it out is completely normal.

Because after 17, Ukrainian uses the genitive plural form of the noun.

• люди = people (basic plural form)
• людей = of people / people after larger numbers

So:

• одна людина = one person
• дві / три / чотири людини = two / three / four people
• п’ять людей = five people
• сімнадцять людей = seventeen people

A useful rule is:

• 1 → usually singular
• 2–4 → a different counted form
• 5+ and 11–19 → usually genitive plural

That is why сімнадцять людей is correct.

кімнаті is the locative singular form of кімната.

After the preposition у / в when it means in, Ukrainian usually uses the locative case:

• кімната = room
• у кімнаті = in the room

So the pattern is:

• у школі = in the school
• у місті = in the city
• у кімнаті = in the room

Both у and в can mean in.

Ukrainian often switches between them for smoother pronunciation. This is mostly about sound, not meaning.

Here, у кімнаті sounds smoother than в кімнаті after людей, because в кімнаті would create a heavier consonant cluster.

So:

• у кімнаті = correct
• в кімнаті = also possible in many contexts

This kind of alternation is very common in Ukrainian.

Yes, you could.

Ukrainian word order is more flexible than English word order because the case endings already show the grammatical relationships.

Both are possible:

• Сімнадцять людей у кімнаті.
• У кімнаті сімнадцять людей.

The second version, У кімнаті сімнадцять людей, often sounds a bit more natural as a neutral there are... statement.

The first version can sound as if the speaker is focusing more on the number seventeen.

A helpful version with stress marks is:

сімна́дцять люде́й у кімна́ті

A rough English-style approximation is:

seem-NAHD-tsyat lyu-DEY oo keem-NAH-tee

A few notes:

• лю sounds like lyu
• ей in людей sounds roughly like ey in they
• the final ть in сімнадцять is soft
• і is like ee in see

Ukrainian does not have articles like a and the.

So у кімнаті can mean:

• in the room
• in a room

The exact meaning depends on context.

English requires an article, but Ukrainian does not.

It behaves like a teen number.

That matters because numbers 11–19 normally take the same noun pattern as 5+, which is why you get людей, not the form used after 2–4.

Compare:

• чотири людини = four people
• сім людей = seven people
• сімнадцять людей = seventeen people

Even though сімнадцять ends in the idea of seven, grammatically it patterns with the teen numbers, so людей is correct.