"Iain and Isabel, do you like the house?"
Translation:Iain agus Iseabail, an toil leibh an taigh?
The short answer is 'with me', 'with you' etc. It is what they call a prepositional pronoun, which just means a preposition joined to a pronoun. But they are synthetic, just like verbs in some languages. Put simply, that means they are irregular and you have to learn them. There is no way to guess from the above how to say 'with her' for example. Le by itself is just 'with' and is also used for belonging and ownership. So you are saying 'thanks with you' or 'thanks belonging to you'.
Toigh means 'agreeable, pleasant' so An toigh leibh an taigh? (to give the original spelling) means 'Is pleasant with you the house?'
Toil is a word that sounds similar in this sentence, and for some reason that is beyond my comprehension, got accepted as the standard spelling. So use it but you will often see the more logical toigh as well. D
For a simple practical reason, nothing to do with whether it is a valid translation:
It is simply that it is a lot of labour for the volunteers who write the course, just to put in all the valid answers with one word order. It would literally double the labour if they allowed arbitrary reversals of the two parts. So however valid the translation, please don't do it unless there is a good reason - such as it being a requirement of the language you are translating into.