This is not a homework but just doing some review before my exam.

My question is:
1) How to find/solve for Voltage across Independent Current/Voltage Source?
-I'm stuck here because I can't apply Ohm's Law. What formula or method should I use? Please kindly explain to me.
2) Current of a Voltage Source.

 

hi JL,
This link should help.
https://www.allaboutcircuits.com/worksheets/superposition-theorem/

E

 

The voltage across an independent voltage source is, by definition, the voltage of the source. If you have a 15 V source, then the voltage across it is 15 V.

To find the voltage across the independent current source, analyze the circuit and solve for v1. The voltage across the current source is (v1 - 0V) = v1.