> Can anyone pinoint me where I made a mistake?

Well, I can try to explain why you are getting your error, or I can
tell you what *really* went wrong...  :)

The main problem, the part that is confusing me (and you, I think,
though you might not know it yet) is this part:

    class Accounts < Account

From what I gather, you are saying that a set of two accounts is a
"kind of" an account.  This is not really the relationship you want to
express, though.  Accounts "has multiple of" Account.  (In general, I
find that there are very few places in which you want to use
inheritance when you are starting out... I can't remember the last
time I used it outside of writing GUI code.)

So, without giving away too much (because sometimes less teaching
means more learning :) I'd say try again, but make Accounts it's own
class (no inheritance) with either two instance variables set to
Account.new(whatever), or an array of accounts, or even a hash with
something like {'checking' => Account.new(something), 'savings' =>
Account.new(something_else)}, depending on how you see it being used.

And definitely let us know if you get stuck again!  It's hard to know
how much to "give away", but we're always happy to help.

Happy Rubying,

Chris