In Chapter 1, how does Pony react to what Sodapop tells him about Darry?By tonight please!
Pony does not understand that Darry is trying to serve as the adult of the household and believes that his oldest brother envisions him as "just another mouth to feed and somebody to holler at." Pony doesn't believe Soda when he tells him that he treats him differently because "you're the baby," and he can't believe Soda when he tells him how much Darry loves him. Pony believes that Darry loves nothing or no one--"except maybe Soda"--and he tries to convince himself that he could care less. But he admits (to himself) that he lies to himself all the time. Deep down, Pony loves Darry, but he has trouble pinpointing exactly why, since Darry rides him all the time.
In Chapter 1, Ponyboy has been jumped by the Socs and rescued by the rest of the Greasers. In the part of the chapter that I think you are talking about, Soda and Ponyboy are in bed later that night. Soda tells Pony that Darry only yells at Pony because Darry has too many responsibilities. He tells Pony that Darry is really very proud of how smart Pony is and that Darry loves Pony a lot.
Pony basically does not believe what Soda says. He just says "Sure," and tries not to sound too sarcastic so he won't hurt Soda's feelings.