Determine all partial currents. Please be very detailed.
I1, l₂, I3, I4, I5, I6, I7
U1=90V, U2=20V, U3=95V, R1=10Ω, R2=20Ω, R3=30Ω, R4=40Ω, R5=50Ω, R6=60Ω, R7=70Ω