"Do you like Wales?"
Translation:An toil leat a' Chuimrigh?
Nitpicking: since there is no bi verb (no a bheil or nach eil) in the question, you wouldn’t answer tha here. For simple yes you’d rather just say is toil or ’s toil.
To answer with full sentence and not repeat the is toil part you could start with seadh: seadh, is toil leam a’ Chuimrigh indeed, I like Wales
seadh comes from older ’s eadh, is eadh, lit. it is (with very archaic neuter pronoun eadh not used in the language anymore except for a few phrases, like seadh), which originally was used to answer questions involving an eadh…? (is it?, is it so?) – but I believe that even such questions are now archaic, and seadh is generally used as aye, yup, indeed, agreeing with some information, not as yes when answering any questions
Although, I’d very appreciate native speakers’ input on the use of seadh, an eadh, chan eadh (or more Irishy ni h-eadh), etc. in modern language – Irish still uses them quite a lot, but from what I can see about Gaelic, only seadh is still used today?