How would you reply to Qué estás haciendo?

Here are some ways you could reply to "Qué estás haciendo?" (What are you doing?), depending on the context:

Formal:

* Estoy trabajando. (I'm working.)

* Estoy estudiando. (I'm studying.)

* Estoy descansando. (I'm relaxing.)

* Estoy esperando a [someone/something]. (I'm waiting for [someone/something].)

Informal:

* Nada mucho, ¿y tú? (Not much, what about you?)

* Estoy [verb + -ando]. (For example: "Estoy comiendo" - I'm eating)

* Chillando. (Relaxing/hanging out)

* No mucho, ¿y tú? (Not much, what about you?)

Humorous:

* Tratando de evitar el trabajo. (Trying to avoid work.)

* Existiendo. (Existing.)

* Pensando en la vida. (Thinking about life.)

You can also add a follow-up question:

* ¿Qué estás haciendo tú? (What are you doing?)

* ¿Y tú? (What about you?)

It's important to choose a response that is appropriate for the situation and your relationship with the person asking the question.