2 sophomores for every 3 juniors:
15 juniors
15/3 = 5
5 x 2 = 10 sophomores
3 freshmen for every 5 sophomores.
10/5 = 2
2 x 3 = 6 freshmen
15 juniors and 6 freshmen
15-6 = 9
There are 9 more juniors than fresh men
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