ANSWER
30 students
EXPLANATION
The cost per student varies inversely as the number of students.
Inverse proportion is written as:
Let the cost per student be y.
Let the number of students be x.
It will cost each student $250 if 24 students attend. This means that:
If the cost is down to $200, it means that y is now $200.
That is:
Therefore, 30 students could attend.