Answer:
El Boleto
Step-by-step explanation:
(Quiero) (viajar) (por) (avión) (a ecuador) (y necesito) (comprar) ________.
(I want) (to travel) (by) (airplane) (to ecuador) (and need) (to buy) [a] ________.
El means "The," specifically used to refer to a "male" word (ending with o or e). Boleto on the other hand, means ticket. You need a ticket to board an airplane, ergo, you need el boleto.