For this case we have:
x: Variable representing the types of advance input
y: Variable representing the same-day entry types
We have according to the cost:

According to the number of tickets:

We have a system of two equations with two unknowns:

We multiply the second equation by -35:

We add:

Thus, 40 same-day tickets were sold.

20 advance tickets were sold
Answer:
20 advance
40 same-day