It's unlikely you would get a ticket for speeding unless you were pulled over by a police officer, at least in the United States. I haven't heard of any camera based speeding tickets. Perhaps someone from Washington can confirm that is the case there.

Is this a ticket from the state or county, or a bill from the rental car company? The rental car company may well try to screw you over with their own usurious "fees."

Too many unanswered questions.