Like I said, it is usually several things together that help determine if a garment is vintage. When buying online, one has to rely on the information that the seller is giving, in photos and in the description, and if that information is not conclusive, then one might have to ask for more questions. A good seller will understand that. When you are buying in person in a shop it's different - you can handle the clothes, try them on and it's easier to get a feel if something might be vintage. But online, you have to rely on these things, and when dating items here in the forums, we need the same kind of information - unfortunately we cannot know everything either!
I can really not say about the blouse. The pants could be vintage as the label corresponds to one we have in our Label Resource that I linked above, but I find it hard to determine much more. A photo showing the pants and their shape in full would help, as might a care label if present. As I said before, it is usually more than one clue that leads to the answer. Some things may be very recognisable in style/shape that one can say immediately it must be vintage, but with a brand like Benetton that also does a lot of classic styles, it can be harder - and so more information may be required.
