For this question we have to set up a system of equations.
Let
A= number of adult tickets
S= number of student tickets
then:
[tex]\begin{gathered} A+S=200 \\ 8S+10A=1760 \end{gathered}[/tex]Solving the first equation for S ans susbtituting S in the second equation we get:
[tex]\begin{gathered} S=200-A \\ 8(200-A)+10A=1760 \\ 1600-8A+10A=1760 \\ 2A=160 \\ A=80 \end{gathered}[/tex]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
[tex]15A+8S=15(80)+8(120)=2160[/tex]Answer: $2160.