help with applied calculus

Assume that a demand equation is given by q = 5000 - 1oop. Find the marginal revenue for the given production levels (values of q). (Hint: Solve the demand equation for p and use R(q) = qp).

I've been out for a couple weeks at school because I was sick and I couldn't find efficient youtube videos to help me out with this. I kind of understand it but I don't know where to start.