R23=R2+R3=60+60=120 Ом
R234=R4*R23/(R4+R23)=60*120/(60+120)=40 Ом
Rэ=R1+R234=60+40=100 Ом
I1=E/Rэ=15/100=0.15 A
U1=I1*R1=0.15*60=9 B
R23=R2+R3=60+60=120 Ом
R234=R4*R23/(R4+R23)=60*120/(60+120)=40 Ом
Rэ=R1+R234=60+40=100 Ом
I1=E/Rэ=15/100=0.15 A
U1=I1*R1=0.15*60=9 B