I like playing blackjack, I might go to a casino one day and try to win a lot of money.
I've played blackjack before.  It is also known as twenty-one. All the players compete against the dealer. 
How long has it been around for?
Good question.  I have no idea. But there are different ways of playing it around the world. In the U.S. the dealer is dealt two cards.  One up and one down. 
What are some other ways of playing it?
I don't know. Another type of gambling card game is community poker.  That where the cards are all dealt face up and placed in the center of the table. 
What is the oldest card game do you know?
Card game
A card game is any game using playing cards as the primary device with which the game is played, be they traditional or game-specific. 
Countless card games exist, including families of related games (such as poker). A small number of card games played with traditional decks have formally standardized rules, but most are folk games whose rules vary by region, culture, and person. 
A card game is played with a "deck" or "pack" of playing cards which are identical
Blackjack
Blackjack is the American variant of a globally popular banking game known as Twenty-One, whose relatives include Pontoon and Vingt-et-Un. It is a comparing card game between one or more players and a dealer, where each player in turn competes against the dealer. Players do not compete against each other. It is played with one or more decks of 52 cards, and is the most widely played casino banking game in the world. The objective of the game is to beat the dealer in one