Discrete Math - Binary Tree

[ResidentBiscuit]

Ok so I'm having a hard time understanding how to construct a binary tree given some characteristics. For example, I have a problem here:

Construct an expression tree for the Polish notation expression
* + B D - A C


And...

Construct a binary tree for which the preorder listing of vertices is:
C, B, E, D, A
and the the inorder listing is
A, C, D, E, F, B, G, H

I understand how to GET the listings from a tree, no problem. And I can get Polish and reverse Polish notation just fine as well, but for some reason I can't do it backwards. Anyone have some tips?

[hanst99]

The first two:

*
  + 
     B
     D
  - 
     A
     C

C
  B
    E
    D
  A

You really just have to do it backwards - there isn't much you'd really need to wrap your head around.