The set of equations from the assigned problem will vary, here is one possible set.

(13)V1R1I1R3I3=0
(14)R2I2V2+R3I3=0
(15)V2V3R6I6+R5I5=0
(16)R4I4R5I5=0
(17)V4R4I4=0
(18)I1I2I3=0

This set of equations can be converted to the following matrix equation:

(19)[R10R30000R2R30000000R5R6000R4R50000R400111000][I1I2I3I4I5I6]=[V1V2V2V30V40]

The answers are

(20)I1=0.091
(21)I2=0.455
(22)I3=0.364
(23)I4=1
(24)I5=0.8
(25)I6=0.5

It should be noted that for the circuit in the second figure, currents I1 through I3 are the same as for the first figure, and it may be interesting to discuss with students why that should be the case.