Translation:I will have an old house but it will be pretty.
Great question! In English we have "will", "shall" and "going to" (like the Spanish "voy a").
I believe that "shall" implies a future act that is compelled or otherwise outside of one's control. "Will" implies a future act of choice. So legal documents use "shall" for acts that are required by law.
There was an old English grammatical joke that went: 'A foreigner falls off an English ship and in desperation shouts out "I will drown! No-one shall save me!". So everyone did as he stated -- and ignored him.'
Cruel, pedantic, but it helped me remember! I'm not sure how "shall" is expressed in Spanish legal documents.
Duo mixes them up in almost every other example, so I don't see why they would count that as wrong.
I like to keep them separate, and not use them interchangeably.
I think the future tense (which isn't used all that much in Spanish) has much more force behind it - I WILL go to the store tomorrow. It seems to be more emphatic.
The ir + a/going to construction is less strong, in my opinion. We're going to go to the store. It's not as "dramatic" as the future tense.
I will =/= I am going to
They're not always interchangeable in English. There's a very subtle difference between the two. 'Going to' implies either a decision made at the time of speaking or plans that have already been made. 'Will' is more general. Compare a woman telling her husband during an argument: 'I'm leaving' or 'I'm going to leave' with 'I will leave'.
Well, it was more of a typing error, wasn't it? I mean, you wouldn't make that mistake if you were speaking. It has let me off with what it calls 'typos' in the Spanish, so I don't see why you should have been penalised for a similar error in English. Ours not to reason why, dadexter.
I put "I will have an old house but it will be pretty." Duolingo counted it wrong and said it should have been "I will have 1 old house but it will be pretty." Then I get to this discussion page and it says the correct translation is "I will have an old house but it will be beautiful." Why in one case was una interpreted as 1 and another time as "an"??