When Daisy asks her friends what they will do for the next 30 years, how does this show the differences between Daisy and Gatsby?
Daisy says this in chapter 7 before the group (Daisy, Tom, Gatsby, Jordan, and Nick) goes into the city. The tone of this conversation indicates that Daisy is not looking forward to the future, perhaps because for her, the future is simply a repetition of her current life, i.e., her life with Tom. Gatsby, on the other hand, is very much looking forward to the future because he sees it as a lifetime with Daisy at his side. In this chapter, Gatsby tells Tom that Daisy never loved Tom and that she is leaving him (Tom). Gatsby thinks that all Daisy has to do is tell her husband that she never loved him and then Gatsby will have Daisy as though the five years since their first declaration of love for one another never passed by. Gatsby is dreaming of an impossibility - erasing the past and marrying Daisy in the future while Daisy is much more realistic despite what she says and how she acts.
Perhaps the most ironic statement in the chapter comes immediately after Daisy makes her "...next thirty years.." comment when Jordan reminds her that "...life starts all over again in the fall." Life, for Gatsby, ceases before then.