Q: Determine the voltage Vo by utilizing source transformation method.

Solution:
We have to determine the voltage Vo by applying source transformation method. We can proceed further as
1k is in series along 2k so joint effect =3k

2mA source is in parallel along 3k resistor. Therefore it can be modified to a voltage source of value = 2m x 3k (by using ohm's Law)
= 6 V
Now, 3k resistor will in series along this source as indicated in the circuit below

In the circuit positive terminal of the 6 V battery is linked with the negative terminal of 3 V battery therefore they will be summed up as indicated in the circuit following

By applying voltage division rule we will get

Vo = (6 x 9)/9
= 6 V Ans.