Respuesta :
Answer: you distinguish between formal and informal greetings by who you are talking too
Explanation: such as formal language is used for things that are professional such as talking too your teacher , informal greeting is talking to your friends or a cousin
using “tu” in spanish is informal, you would use this when talking to friends or acquaintances. using “usted” in spanish is the formal of “tu” and you would use this when speaking to grandparents , teachers , parents , etc