A Juan le gusta la silla

A Juan le gusta la silla
 

A Juan le gusta la silla
A ella le gusta la silla
.
A Juan
A ella - let me specific about who likes the chair

My question is this:

How do I say?

What does he like to do?
What does Juan like to do?
What does she like to do?
What do they like to do?

In each instance I would like to be specific(not just from context) who I am talking about.I appreciate your help,I'm very confused at the moment.Thanks a million.

You might try seeing what you can do with statements before turning them into questions. What do you think would work for these statements?

He likes to do that.
Juan likes to do that.
She likes to do that.
They like to do that.

Once you can make sense of that, you can figure how to change "that" to "what", and perhaps have an easier time understanding how it all works.