Answer:
A mi amigo LE gusta vivir en las afueras de la ciudad.
Explanation:
The verb gustar (to like) has a different conjugation form than the regular ones. The verb combines with the object (a thing or a person we like) and not we the subject.
A mí me GUSTA Ana.
Gusta is singular because the object is ONE.
A mí me GUSTAN Ana y Pablo.
Gustan is plural because the object is MULTIPLE.
Besides that, we always have to use the indirect object form for the subject.
a mí ME a nosotros NOS
a tí TE a vosotros OS + gusta/ gustan
a él LE a ellos LES
In this example, the missing word is LE because mi amigo is ÉL (he). And the verb is gusta (singular) because vivir en las afueras de la ciudad is singular.
