Answer:
To gain $450, they need to sell 90 student's tickets and 30 adult's tickets.
Explanation:
Givens:
- Student's tickets cost $3.
- Adult's tickets cost $6.
- They wanna make $450.
- The auditorium has 120 seats.
Now,
represents adults and
represents students.
Using these variables and all costs given, we have the following expressions:
; this expresses the total earning they want to make.
; this shows the capacity of the auditorium, it's distributed between adults and students, which are the two types of tickets.
Now, we have to solve this system of equations to find the value of each variable.
Observe, if we multiply the second equation by -6, we could eliminate one variable and find the other one's value:

Then, we replace this value to find the other one:

Therefore, to gain $450, they need to sell 90 student's tickets and 30 adult's tickets.