R2 is in parallel with R3 and R4
R2= 10 ohm
R3= 5 ohm
R4= 15 ohm
Req 34 = 5 + 15 = 20 ohm
Req 2,3,4 = 10 * 20 / 10 + 20 = 6.67 ohm
Ohm's law = V = I * R
V 2,3,4 = 3A * 6.67 ohm = 20 V
R eq = r1 + r eq 2,3,4 = 25 ohm + 6.67 ohm = 31.67 ohm
V 1 = I * R = 3 A * 31.67 ohm = 95 V
VT = V1 + V 2,3,4 = 20 v + 95v = 115V
To find I2 :
V = I * R
I2 = Veq / R2
I2 = 20 / 10 = 2 amp
V2= I2* R2 = 2 * 10 = 20 v
Using Kirchhoff's law
I3 = I4 = I1 - I2 = 3 A - 2 A = 1 A
Again Ohm's law for V3 and V4
V3 = I3 * R3 = 1 * 5 = 5V
V4= I4 * R4 = 1 * 15 = 15 V
IT = VT