So, the number of students in Band, Art, Music and Journalism are 2n, 7n+6, 4n-2 and 2(4n+6) respectively.
Since the number of students enrolled in Art and Music is equal to the number of students enrolled in Band and Journalism, we have the equation
7n + 6 + (4n-2) = 2n + 2(4n+6).
We now expand the brackets :
7n + 6 + 4n - 2 = 2n + 8n + 12
-> 11n + 4 = 10n + 12
-> 11n + 4 - 10n - 12 = 0
-> n - 8 = 0
-> n = 8.
Therefore, the number of students that enrolled in :
Band : 2n = 16 students.
Art : 7n + 6 = 62 students.
Music : 4n - 2 = 30 students.
Journalism : 8n + 12 = 76 students.
76 = 16 = 62 + 30 = 92, satisfying the requirement.