I'd like to know why in the chapter Six of The Great Gatsby, the narrator says that "somebody brought Tom Buchanan in for a drink" if, in fact, Tom Buchanan was accompanied by two people. I thought that "somebody" was used for one person only. Could it be used for several people?
"I hadn’t been there two minutes when somebody brought Tom Buchanan in for a drink. I was startled, naturally, but the really surprising thing was that it hadn’t happened before.
They were a party of three on horseback—Tom and a man named Sloane and a pretty woman in a brown riding habit who had been there previously."
You are right in that "somebody" has to refer to one person. In this case, I would suggest that the one person is Gatsby. Consider the context for a moment. Nick has finished his reflection about Gatsby's past. In breaking that memory into the present tense, Nick watches as the three people- the woman on horseback, Sloane and Tom- are welcomed by Gatsby, himself:
They were a party of three on horseback--Tom and a man named Sloane and a pretty woman in a brown riding-habit, who had been there previously.
"I'm delighted to see you," said Gatsby, standing on his porch. "I'm delighted that you dropped in."
As though they cared!
When Gatsby says that he is "delighted to see" them, it reflects that he himself had invited them for a drink. He had been expecting them, anticipating their arrival. Gatsby is the "somebody" that Nick describes. Gatsby is the individual that invited Tom because Nick refers to this point later in the chapter. Describing Gatsby as being "profoundly affected by the fact that Tom was there" and then later describing Gatsby as "moved by an irresistible impulse" to talk to Tom, who "accepted the invitation as a stranger," it becomes clear that Gatsby is the one who invited them to his home. In an "aggressive" manner, Gatsby begins to question Tom about Daisy, almost in a way to examine his "competition" in trying to win her for himself. It is Gatsby who is the "somebody" that has invited the three guests. He did so to see if he could be able to overcome Tom's presence in Daisy's life.