A Ms. Monti bought 4 adult tickets and 3 children's tickets.
The ordered pair (4, 3) represents the number of adult tickets and children's tickets that Ms. Monti bought. Since the equation 25x + 15y = 145 is true when x = 4 and y = 3, this means that Ms. Monti bought 4 adult tickets and 3 children's tickets, and spent a total of $145.