I have attached a pdf of the problem I am working on. The top circuit is the original problem; I am supposed to solve for the voltage drop across the 4-ohm resistor (top right). I HAVE to use the superposition theorem to solve this problem. The 4 circuits drawn below the top circuit are where I eliminated the current source in an attempt to solve for the currents/voltages on each resistor. Can someone please check my work thus far and let me know where I made a mistake? I think there is a mistake because when I take I*R fr each resistor and add them up, I get 28V which doesn't equal my 20V source. Thanks in advance for your help!
The Attempt at a Solution
See attached pdf.