Answer:
I am not certain what you need, it is straight forward.
a. Figure open circuit voltage Vab. That seems easy...you have V3+V2 equal to Vs Remember V3 has two currents thru it, 20ma + the current due to Vs. Vab= V3
Next, find short circuit current, you have Iab=I2-20mA
given that, you can deduce the Thevelin equivalent directly.
