Is there any more information given? you need to add up the cost of each ticket, so for instance if each ticket for the roller coaster is $10, they would need $20 so they can get two tickets so the both of them can get on... and if the tickets for the bumper cars are $5 each, they would need $10 so they can get two tickets so they both can get on the bumper cars as well...
Just apply this equation when you figure out how much each ticket costs.
x= cost of the ticket
y= total cost
x(2+2) = y
