4. In two groups, there is an equal number of students. Each student studies at least one language: English or French. It is known that 5 people in the first group and 5 in the second group study both languages. The number of students studying French in the first group is three times less than in the second group. The number of students studying English in the second group is four times less than in the first group. What is the minimum possible number of students in one group?
4. Let the number of people studying French in the first group be $x$, then in the second group it is $3x$. Let the number of people studying English in the second group be $y$, then in the first group it is $4y$. The total number of people in the first group is $x+4y-5$, and in the second group it is $3x+y-5$. By equating these values, we get $3y=2x$, from which it follows that $y$ is an even number. Note also that $y \leq 5$, since if 5 people study two languages, then at least five people study English. From this, it follows that the minimum value of $y=6$, then $x=9$, and the total number of students in one group is $x+4y-5=9+24-5=28$ students.

Answer: 28 students.