I've never seen "a" used as "to" instead of "the" before. What are the rules for using an article before the infinitive?
Hmmm.... hard to explain... i think itll be more useful to learn how to use them in context. When someone/something is supposed TO do something, use TO as A
Could you also substitute "para" for "a" in this situation?
I many cases, yes. When the meaning is an objective/goal, a and para means the same.
Just remember that it's not an article, it's a preposition.
i put "this" instead of "that" for "isso". :|
It did not accept "that is a lot to think about", even though in English it means the same and is probably more common.
I agree with David52846, "That's a lot to think about" should be accepted. There may be a small number of cases in which they're not interchangeable, but to my (American) ear they mean essentially the same thing.
I did the same... and didn't accept it. But on second thought, I think it is not exactly the same. It's just a different work in both languages.