Find voltage for circuits with buffer amp

[rzn972]

Homework Statement

Homework Equations

The Attempt at a Solution

I first found Vab which was 10 by using voltage division on the first device. By connecting CD to AB, the equivalent resistor is 80// 20, 16? I am not sure where to go from here.

 

[gneill]

Your life would be made easier if you first reduced Device #1 to its Thevenin equivalent and Device #2 to a single equivalent resistance. For part (2) draw the resulting circuit using your simplified device models.