a. \(R=R1+R2=3+6=9\Omega\)
b. \(I=I1=I2=U:R=12:9=\dfrac{4}{3}A\left(R1ntR2\right)\)
c. \(\left\{{}\begin{matrix}U1=I1\cdot R1=\dfrac{4}{3}\cdot3=4V\\U2=I2\cdot R2=\dfrac{4}{3}\cdot6=8V\end{matrix}\right.\)
d. \(\left\{{}\begin{matrix}P1=U1\cdot I1=4\cdot\dfrac{4}{3}=\dfrac{16}{3}\\P2=U2\cdot I2=8\cdot\dfrac{4}{3}=\dfrac{32}{3}\\P=UI=12\cdot\dfrac{4}{3}=16\end{matrix}\right.\)(W)