"Do you usually write letters?"
Translation:Brukar du skriva brev?
So vanligtvis is the adverb, vanligt is an adjective only for ett-words and brukas is like some kind of verb that means the same... like you said in the previous comment to zk1P4. So, if I get it properly, "Skriva du vanligt brev?" would mean something like "Do you write common letters?" Is that my mistake?