I'm reviewing for a test and can't find anything in my notes or book to explain this review problem, wondering if anyone can help.

Given x = 2t, y = 2t² + 3t

a.)find: dy/dx, when t = 2

b.)dy/dx at the point (2,5)

I understand that in a.) I have to substitute 2 for t, just not sure when/where to substitute it... do you calculate dy/dx and then plug 2 in for t? and for b.) I know that t = 1 for point (2,5) but no clue what it means to find dy/dx at that point. Any help will be appreciated and a brief explanation if possible, the answer won't do me any good if I don't know how to do it =)