That is what I thought as well! But according to DuoLingo it's not correct?
If more than one legal persons have to sign something, and apenas it's your turn, it is totally appropriate to add the 'eu', so I dare to think.
There is a mistake on the answer. "Where ca I write"? This is an obvious omission, which has to be corrected pronto.
is there a word for do - in a lot of sentences that duolingo put up the do is just implied -is that how it works? I cant think of examples but it has happened in other categories as well
In "where do I write?" "do" is an auxiliar verb - it indicates the present tense. In "I do that", "do" is the main verb - it indicates the action in the sentence. Same word but with different functions.
Latin based languages - so that includes Portuguese - do not have this first "do"; The only "do" we have is the verb "fazer" that always works as a main verb, never as an auxiliar.
As far as I'm aware in Latin based languages they don't use "do" in the same way we do in English. In Portuguese "fazer" means to do/make and it is only used in this context. English is the weird one here...