Thevenin equivalent E
One way is to do the thevenin twice.


the circuit with 110V source, 165R, 110R and 55R. Output R = 220 in parallel with 110 = 73.33R Offload V = 36.67V
Add the remaining circuit. We have 36.67V source in series with 73.33 + 55 + 55  = 183.33ohms. This is potted down by the 110R Output R is 183.33 in parallel with 110 = 68.75R Vout offload = 36.67 / (183.33 + 110) * 110 = 13.75V


Answer: Equivalent = 13.75V + 68.75ohms