Be a Mad Person

I am a MAD Person. I mean Mathematical Ability Developing Person. I wish all of you to become MAD persons.
To begin with how to scratch your brain ( Boolean Randomized Algebraic Integral Numero nerves - explain this if you can !) to show you the beauty of Mathematics in my forthcoming blog articles, i shall raise the following questions.
Question no 1.
The definition of a set given by George Cantor was disproved by Betrand Russell. So could you define a set?
Question no 2.
Why a tripod has only three legs?
Question no 3.
What is the role of DS1 in the mathematics world? (that is in which context the term DS1 is used in mathematics? (or the relation between DS1 and Mathematics)