Let the number of student tickets sold be s and the number of adult tickets sold be a.
(a) 10s+12a=146
(b) 15s+8a=139
(c) Multiplying the bottom equation by 1.5, we get
. Subtracting this from the first equation, we get that
, and thus s=5. So, if s=5, this means
, and thus a=8.
So, a student ticket costs $5 and an adult ticket costs $8.