Let me give you a hint on what I mean:
Your assignment contains expressions like "a positive transition", "a
negative transition" and "any transition".
These are basic matters in digital design and the verilog language as
well.
You may:
a) not know how to express these "things" in verilog. -> I suppose that
you either noted syntax and meaning of that things during lessons or
read it in a book (or any paper your teacher gave out). In such case,
read it just again. If you still don't understand that, cite the
questionable sentence(s) and explain what detail isn't understood by you
or seems to impose contradictions to any of your other assumptions about
the matter.
b) actually not know how to "combine it" (form a proper sequence)
syntactically with other verilog expressions in a way which makes them a
precondition for the desired ouput. -> This is in essence the same case
as a, but you may face unforeseen, unconsidered implications in this
very case which worry you. -> Then it would be appropriate to show us
your attempt and your difficulties (i.e. error messages).
Hope that explanation helps to clarify the issue.