Part A and B I got the same answers. For part D I think you would have to do part C first in my opinion because, in that circuit the total resistance is 4.5 ohms with 9 volt battery. The 3 ohm resistor is in series with the parallel combination of total resistance 1.5 ohms. What I would have done was used a ratio technique there by dividing the battery voltage by the total resistance and multiplying it by the 3 ohm resistor to calculate the voltage across V1. However, correct me If I'm wrong because I haven't done a question like this in a while....