How to find Vs in this circuit with current and voltage sources
Draw the circuit and simplify it in steps, as shown below:







simulate this circuit &ndash; Schematic created using CircuitLab

The blue arrows show you the steps I took here. The first step just reordered the two voltage sources in order to get the resistors into position for easier understanding. The next step combines the resistors (no harm in doing so.) The final step sets a "ground point" (which you are allowed to do in exactly one place.) Then, by definition, you also know that there is a virtual ground up at the top of the current source, of course, as you point out must occur.

I would imagine this would be pretty easy to solve now.

Is this sufficient help?

Or are you looking to just "stamp out" rote mathematics to achieve the same thing?



Noting your comment:


  "I'm just a little confused how you can just switch around the
  voltages and the resistors to get them in series. Doesn't the original
  problem show the resistors in parallel?"


The \$2\:\Omega\$ and \$3\:\Omega\$ resistors are not parallel. They are in series. Similarly, the \$6\:\Omega\$ and \$8\:\Omega\$ resistors are not parallel. They are also in series. Let's look at the first schematic (upper left corner) again, and then the transformation moving to the right upper left corner (from above):







simulate this circuit

No difference at all from the earlier examples above. But now they look like they are in series.

You need to break yourself of the idea that if two resistors are drawn parallel to each other on paper, then they must be in parallel as far as a circuit is concerned.

A schematic drawing is just the way a human draws something in order to (hopefully) communicate accurately with another human. But like any other communication between humans, it's possible to lie, dissemble, and be disingenuous. To trick you or to pull the wool over your eyes, so to speak. Though sometimes it's just a matter of having the time to draw out a tight schematic that communicates well. As Bjarne Stroustrup has been quoted,


  "I would have preferred this paper to be either much longer or much
  shorter, but I did not have the time to do either."


Part of learning circuitry is learning how to tear down someone else's "statement" and taking the time needed for rebuilding it back into something that communicates better.

To paraphrase from Dr. Rudolf Flesch in his book, "The Art of Plain Talk," as an example of bad writing:

"An ultimate consumer as used here means a person or group of persons,
 generally constituting a domestic household, who purchase eggs generally
 at the individual stores of retailers or purchase and receive deliveries
 of eggs at the place of abode of the individual or domestic household
 from producers or retail route sellers and who use such eggs for their
 consumption as food."


Clearer is,

Ultimate consumers are those who buy eggs to eat them.


It's the same way with schematics.