.
x tickets        at the price $12.50, and
(415-x) tickets  at the price  $8.00.
Write the total cost equation
    12.50x + 8*(415-x) = 4085  dollars.
Simplify and find x
    12.50x + 3320 - 8x = 4085,
    12.50x - 8x = 4085 - 3320
         4.50x  =    765
             x  =    765/4.50 = 170.
ANSWER.  170 tickets at the price of $12.50  and the rest, 415-170 = 245 tickets at the price of $8.
CHECK.  12.50*170 + 8*245 = 4085,  total cost.  ! correct !
Solved.
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To see many other similar solved problems using one equation in one unknown,  look into the lesson
    - Typical problems on buying and selling items 
in this site.
To see many other similar solved problems using systems of two equations in two unknowns,  look into the lesson
    - Using systems of equations to solve problems on tickets 
in this site.