Where do I best learn informal set theory?

Question

I want to learn math for machine learning, and I want to start with informal set theory.

I was reading 'naive set theory' (1960) by halmos, and it didn't seem to contain modern set notations.

If anyone knows a good material for learning informal set theory, please leave a comment.

That being said, I do not mind some rigor as long as it helps me with statistics, calculus, and other math fields used in machine learning.

Answer 1

You can see the book "Book of Proof" of Richard Hammack; it have many diagrams and pics. The chapter about cardinals is very educational.

P.S.: Machine leaning is more about Linear Algebra and Probability Theory.

Answer 2

Have you already had a look at this: Khan Academy: Set Theory