V is the difference between potentials at two places in the circuit.
If you look at the voltage sources, the top is less positive than the bottom - so the bottom must have a higher potential than the top. Replace the voltage sources with an equivalent single voltage source and the answer to your question will become clear.
Note: when you do kirkoffs laws to analyze a circuit - draw voltage arrows on the components as well as current arrows at the nodes.
Did you solve the problem?
I'm asking because if you didn't, can you tell just by looking it that it will be negative?
Yes, I can tell just by looking; But I've looked at a LOT of circuit problems over the years!
I took note of the two voltage supplies and determined that the top of them will be negative w.r.t. the bottom. I then looked at the polarity specified for "measuring" the output and drew the conclusion that Vout must be negative.