how are Tom and Daisy part of the established upper class
Throughout Fitzgerald's The Great Gatsby, we see numerous examples of the tension between people from different social classes--more specifically the rich (or "old money") vs. the poor (or "new money").
But, one difference between these classes is that the rich possess a resilence despite any circumstance. The rich in Fitzgerald's world (Tom and Daisy) can afford to be silly, reckless, and in this story, even murderous and get away with it. However, when anyone from a lower class participates in these shenanigans, they pay for it with their reputation, money (or in Gatsby's case, his life). The rich in this story walk around with a safety net, and they are exempt in many ways, from consequences.
After Gatsby's death, Nick runs into Tom on the street where they have a short argument about what happened. When Nick realizes it's useless, he says to himself
They were careless people, Tom and Daisy — they smashed up things and creatures and then retreated back into their money or their vast carelessness, or whatever it was that kept them together, and let other people clean up the mess they had made. . . . (chapter 9)
Nick understands that people like Daisy and Tom don't care, because nothing can touch them. Nick also realizes that Gatsby, and others like him, will always be vulnerable because of their place on the socio-economic ladder.
Tom and Daisy Buchanan are married couple in the book "The Great Gatsby". First let's look at Tom.
Tom Buchanan is a very rich, wealthy man. He's a selfish person who does what he has to, to get what he wants. Tom is also very athletic. Although we never see it, he has a temper, especially with his wife. Daisy tells us of a bruised finger, that, although it was an accident, was caused by Tom.
His wife, Daisy, is an old flame of Jay Gatsby. Gatsby basically builds his fortune and his whole career on hopes that someday he and Daisy will get back together again. Daisy is a sassy, fun loving flirty, but charming woman. Even when she speaks, her voice sounds as if she's loaded with money, and an intriguing sexiness, that draws the listener, and even the characters towards her.
Tom and Daisy are part of the established upper class because they are from "old" money. They have grown up with money and they have inherited their money. Both of these characters are well-to-do and married each other accordingly... Daisy was unable to be in a relationship with Gatsby due to his poor status; therefore, marrying Tom seemed to be the right thing to do. They went to the appropriate schools for the wealthy and are friends with the appropriate people.