Hey guys, I'm in System Dynamics and have been given a fairly fundemental problem to work on.

It states: can also be written . It then instructs me to derive equations for C and D in terms of A and B. I know this is pretty fundemental, I also know that , and but I do not want to confuse deriving an equation with substitution.

I'm not looking for an answer or anything like that, I just need someone or several people to put me on the right path. I'm not quite sure where to start. Thank you.