"My house has a blue roof."
Translation:Mi casa tiene un techo azul.
Why is 'un' used in "my house has a blue roof" and 'el' in "his house has a grey roof"?
Un techo - a ceiling/roof.
Mi casa tiene un techo azul - My house has a blue roof.
Su casa tiene un techo gris - His house has a grey roof.
I think they just corrected their mistake. They are probably both accepted now.
That's what I thought but when I typed "Su casa tiene un techo gris" it maked me wrong and corrected it with "Su casa tiene 'el' techo gris", but "Mi casa tiene un techo azul" was correct. I can't figure why.
I'm not sure either, but then the Spanish rules on when you need to use the definite/indefinite article, the, a, an in front of a noun and when you don't is still a bit of a mystery to me!