"Doesn't George have the money?"
Translation:Nach eil an t-airgead aig Seòras?
Tha y aig x is the equivalent of x has y in English - as it's a central construction for Gaelic it's essential for learners to get used to that construction rather than working on direct translations. "Isn't the money with George?" means something different in English from Doesn't George have the money?, and the equivalent sentence in Gaelic (which would be different from *Nach eil an t-airgead aig Seòras") also has a different meaning.
In Gaelic the subject of the sentence is often the object of the equivalent sentence in English and vice versa. In English we say "x has y" or "doesn't x have y" - Seòras has the money/ Doesn't Seòras have the money? - so Seòras is the subject of the sentence.
In Gaelic, we would say tha y aig x (y is at x) or nach eil y aig x? - tha an t-airgead aig Seòras / nach eil an t-airgead aig Seòras, so an t-airgead is the subject of the sentence, rather than Seòras.
agad is a contraction of aig + thu. You would use agad if you were asking "Don't you have the money" - nach eil an t-airgead agad?
If you keep in mind the basic construction "x has y" = tha y aig x you can slot in nouns and names as you like.
If you want to use a pronoun rather than a name for x, "(x=(I/you/he/she/it/we/you/they)) has/have y", you would use the appropriate prepositional pronoun.
Tha y agam - I have y
Tha y agad - you (singular informal) have y
Tha y aige - he/it has y
Tha y aice - she/it has y
Tha y againn - we have y
Tha y agaibh - you (plural or singular formal) have y
Tha y aca - they have y.