Electrical circuit related problem

[Yammy]

Homework Statement

Determine the value of the voltage Vx
across the 3A current source.

Homework Equations

The Attempt at a Solution

I am really confused about how to do it. What I thought of is to find the voltage across the 4 ohm resistance which is 12 V. I though of subtracting that from the power sources.

But I am not sure which power source should be positive and which one should be negative?
Should I just assume the bigger 6V to be positive just because it is the bigger power source?
I might be completely wrong on this one. So please help me. This is not really a homework problem, this is in one of my practice tests, so I would appreciate any proper explanation I can get, rather than vague hints.
Thank you.

 

[Yammy]

Oh and please look at the attachment for the diagram

 

[gneill]

Homework Statement

Determine the value of the voltage Vx
across the 3A current source.

Homework Equations

The Attempt at a Solution

I am really confused about how to do it. What I thought of is to find the voltage across the 4 ohm resistance which is 12 V. I though of subtracting that from the power sources.

Sure, sounds like a good idea. Use KVL around the left loop.

But I am not sure which power source should be positive and which one should be negative?
Should I just assume the bigger 6V to be positive just because it is the bigger power source?

The voltage sources are labeled with their polarities so no need to guess! Just do a "KVL walk" around the loop in either direction and sum up the potential changes as you go. The math will take care of itself.

 

[Yammy]

ya u r right. Got it and thanks a lot.