For this question we have to set up a system of equations.
Let
A= number of adult tickets
S= number of student tickets
then:
Solving the first equation for S ans susbtituting S in the second equation we get:
With the value of A we can get the value of S=200-A=200-80, S=120.
Finally if the adult ticket costs $15 instead of $10 and the student ticket remains the same, then the total earnings would be
Answer: $2160.