Power of sets

[courteous]

What are powers of following sets: ?,{?},{?,{?} },{{?,{?} } } ?

|?|=0, |{?} |=1, |{?,{?} } |=2, |{{?,{?} } } |=1

Correct :?:

 

[pka]

It is a bit hard to read the question.
But yes it appears to be correct.

 

[courteous]

Which part seems to be dubious (would really like to get an accurate answer)?
With "power" I've tried to say "number of elements within a set". Is this a precise terminology?

pka, thank you for responding.

 

[pka]

Which part seems to be dubious (would really like to get an accurate answer)?

I did not say that it was dubious. I said it was hard to read.
You should learn to use LaTeX if you are serious about these questions.
Surely you can agree that \(\displaystyle \left\{ {\left\{ {\emptyset ,\left\{ \emptyset \right\}} \right\}} \right\}\) is easier to read than what you posted.