\(R=R1+\left(\dfrac{R2.R3}{R2+R3}\right)=20+\left(\dfrac{80.80}{80+80}\right)=60\Omega\)
\(I=I1=I23=U:R=12:60=0,2A\left(R1ntR23\right)\)
\(U23=U2=U3=U-U1=12-\left(20.0,2\right)=8V\)(R2//R3)
\(\left\{{}\begin{matrix}I2=U2:R2=8:80=0,1A\\I3=U3:R3=8:80=0,1A\end{matrix}\right.\)