Leo: Premise: "A man who is wearing a maintenance vest is on a subway or train looking up at the closed doors."
Hypothesis: "A man who is wearing a vest is doing maintenance on a subway."
Do we know that the hypothesis entailed by the premise?
Mei: OK, So, let's think first...
Me:
Wearing a maintenance vest on the subway does not mean the man is doing maintenance at that time. He could be a maintenance man on his way home from work or on his way to work or on his way anywhere.
Thus, the answer is it is not possible to tell.