Since each van and each bus carried the same number of students, and each school used same number of bus, that is, 9, the difference in the number of vans used by High School A and High School B is due to the difference in number of students participated from each school, we shall have the number of students that a van can carry from these differences.
The difference in number of students participating = 513-486=27
The difference in number of van used = 5-2 =3
Thus 3 more vans used by High School A than High School B carried 27 more students of High School A than High School B.
Thus each van can carry =27/3= 9 students
Therefore 5vans used by High School A carried their (5*9)=45 students
Therefore 9 buses used by High School A carried their (513-45)=468 students
Since each bus carries same number students, each bus carried (468/9)=52 students for both High School A and High School B
Therefore students of High School B carried by van must be = (486-468)= 18
Since each van carries 9 students, they used (18/9)=2 vans which satisfies given conditions.
Hence a van can carry 9 student. A bus can carry 52 students.