Can you help me find the voltage drop for R3 and R4 on the following circuit
You can solve this without calculating currents at all.

You already did the hard part and correctly calculated R2345 as 3.6R

Now you have a voltage divider with R1 from the 12V, so...







simulate this circuit &ndash; Schematic created using CircuitLab

\$V_{R2} = 12 * 3.6 / 9.6 = 4.5V\$

Since R34 = 3 and R5 is 6, again a simple voltage divider, 







simulate this circuit

\$V_{R34} = 4.5 * 3/9 =1.5V\$