3) R34=R3*R4/(R3+R4)=50*100/(50+100)=33.3 Ом
R234=R2*R34/(R2+R34)=20*33.3/(20+33.3)=12.5 Ом
Ro=R1+R234=7.5+12.5=20 Ом
Io=i1=U/Ro=120/20=6 A
U234=U-I1*R1=120-6*7.5=75 B
I2=U234/R2=75/20=3.75 A
I3=U234/R3=75/50=1.5 A
I4=U234/R4=75/100=0.75 A
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