Riddles about letters

what am Itricky

While I am in air, I am not in oxygen. I am also in water, but not in hydrogen. I am necessary in all animals, but you won't find me in the zoo. Look in all brains and you'll find me there too. What am I?
The Letter A.
67.29 %
93 votes
logicwhat am I

Alone I am 24th, with a friend I am 20. Another friend and I am unclean. What am I?
The letter 'X'. It is the 24th letter of the alphabet, XX in Roman numerals is 20, and XXX is a label for movies that are very inappropriate (unclean).
61.35 %
186 votes