Translation:I am buying either violet or blue trousers.
"I'm" itself is accepted automatically as a contraction of "I am".
The correct translation for "albo... albo", as far as I know, is "either... or", not "either... either".
They would be used in a negative sentence: I don't buy neither violet, nor blue trousers. = Nie kupuję ani fioletowych, ani niebieskich spodni.
"I am buying either violet trousers or blue ones" should IMHO be an acceptable answer. Also, the suggested correction was "I am buying either violet or a blue pants." with "or", "a" and "pants" all underlined. The "a" is, of course, superfluous...
(1) Well, yes, it's wrong, but I don't like to be rude :-)
(1) Don't worry, you can politely say that something is wrong ;) Sometimes someone put a wrong answer, but more likely it's caused by the alternatives put in brackets - [a/the/] for example work, I believe, with "pair of trousers" here, but not if we omit "pair of" and that's what caused this specific error.
I can't see why "I'm buying either violet or blue trousers" is wrong, when this has exactly the same meaning as "I am buying either violet or blue trousers".
I'd (I had :-) ) always thought that Duo would accept contractions like "I am" -> "I'm".
This should have worked. But it was added relatively recently, perhaps the changes haven't gone live yet...
I'm buying blue or voilet trousers is wrong but in English isn't the "either" implied in translation. In normal use people often omit the either