Answer:
I believe the answer is Nico las escribe.
Explanation:
Since <em>cartas</em> are plural and feminine (you can determine by the -a ending for the "gender" and the -s ending for singular and plural), the correct direct object pronoun is las. Let me know if you still need help!
La upr, recinto de San Juan
Answer:
She thinks that he is rude and he is quiet.