At the north campus of a performing arts school, 60% of the students are music majors. At the south campus, 90% of the students are music majors. The campuses are merged into one east campus. If 69% of the 1000 students at the east campus are music majors, how many students did each of the north and south campuses have before the merger?

The north campus had $◻$ students.
The south campus had $◻$ students.

Step 1 ：Let $N$ be the number of students from the north campus and $S$ be the number of students from the south campus.

Step 2 ：The total number of students after the merger is 1000, so $N+S=1000$.

Step 3 ：60% of the students from the north campus are music majors and 90% of the students from the south campus are music majors.

Step 4 ：After the merger, 69% of the 1000 students are music majors, which means there are 690 music majors in total.

Step 5 ：This gives us the second equation: $0.60N+0.90S=690$.

Step 6 ：Solve the system of equations $N+S=1000$ and $0.60N+0.90S=690$ to find the values of $N$ and $S$.

Step 7 ：The solution to the system of equations is $N=700$ and $S=300$.

Step 8 ：The north campus had $\boxed{{\displaystyle 700}}$ students.

Step 9 ：The south campus had $\boxed{{\displaystyle 300}}$ students.