Let n be the number of students at the north campus, and s be the number of students at the south campus. Since there are 1000 students on the east campus after they merged, we can write n+s=1000, or n=1000-s. Since 10% of the students at the north campus, 50% of the students at the south campus, and 21% of the students at the east campus, were music majors, we can write.1n+.5s=.21*1000, or.1n+.5s=210. Plugging n=1000-s into that equation, we have: .1n+.5s=210 .1(1000-s) +.5s = 210 100 -.1s +.5s = 210 .4s + 100 = 210 .4s = 110 s = 275 Plug that into n=1000-s: n = 1000 - 275 n = 725 So there were 725 students at the north campus and 275 students at the south campus before the merger. *Note: This implies that the north campus had 72.5 music majors and the south campus had 137.5 music majors, which really doesn t make much sense, so this isn t the best question. I hope that helps :)