How am i supposed to do this problem and what would be the answer

Question

Tickets to the zoo cost $12 for adults and $8 for children. The school has a budget of $240 for the field trip. An equation representing the budget for the trip is 12x+8y=24012x+8y=240. If there are eight adults who need tickets, what is the maximum number of students who can go to the zoo while staying within the school budget? 

Answer 1

[240 - 8(12)]/8= (240-96)/8 = 144/8 = 18 students can fit within the budget

total cost -adult price times 8 adults, then divide by student price to get maximum number of students = 18