Question 271376
N+S=2,000 OR N=2,000-S
10N+7S=17,339
10(2,000-S)+7S=17,339
20,000-10S+7S=17,339
-3S=17,339-20,000
-3S=-2,661
S=-2,661/-3
S=887 STUDENT TICKETS WERE SOLD.
N=2,000-887=1,113 NON-STUDENT TICKETS WERE SOLD. 
PROOF:
10*1,113+7*887=17,339
11,130+6,209=17,339
17,339=17,339