В нашем университете двести студентов.

Because в is the preposition used here for location, meaning in or at. When в means location, the noun after it usually goes into the prepositional case. That is why:

• университет -> университете
• наш -> нашем

Both words change because they must match the case.

Университете is prepositional singular. Many masculine nouns that end in a consonant in the dictionary form take -е in the prepositional singular.

For example:

• университет -> в университете
• город -> в городе
• музей -> в музее

So в университете means in/at the university.

Because adjectives and possessive words in Russian agree with the noun they describe in:

• gender
• number
• case

Here, университете is masculine, singular, prepositional, so наш must also be masculine, singular, prepositional: нашем.

After двести (two hundred), the noun is put in the genitive plural. The genitive plural of студент is студентов.

So:

• двести студентов = two hundred students

This is part of a broader number pattern in Russian. After many numerals, the noun does not stay in the basic dictionary form.

Russian numerals control the form of the noun after them.

A very simplified pattern is:

• 1 -> nominative singular: один студент
• 2, 3, 4 -> genitive singular: два студента
• 5 and higher -> genitive plural: пять студентов

Numbers like двести follow the pattern that takes genitive plural, so you get двести студентов.

Because in this sentence двести is in the nominative case. It is the form used when the numeral phrase is the main noun phrase of the sentence.

Russian numerals do decline, though. For example:

• двести студентов — nominative
• нет двухсот студентов — genitive
• с двумястами студентами — instrumental

So двести is not an unchanging word; it just happens to be in its basic form here.

Russian word order is more flexible than English word order. Starting with В нашем университете puts the location first and sets the scene.

So the sentence feels like:

• At our university, there are 200 students
• In our university, there are 200 students

This is very natural in Russian, especially in sentences that say what exists somewhere.

It can correspond to either in English, depending on what sounds most natural. With университет, English often prefers at in this kind of sentence:

• There are 200 students at our university

But the Russian preposition is still в.

No. In a sentence like this, студентов can refer to students in general, including a mixed group of male and female students.

Russian has:

• студент — male student
• студентка — female student

But in plural, forms based on студент are very commonly used for a general or mixed group.