Yeah, use the voltage divider rule...
You'd get VR1 = [28v (4)] / [4 + (R2//R3)]
then I through R1 = VR1/R1...
and
VR2 = 28v - VR1
then VR2 = VR3 since they are in parallel...
and I of R2 is simply VR2/R2
and I of R3 is VR3/R3...
same goes when you use the 7v...