So okay first thing that I need to do is find the direction of a current in each branch.

I thought that there is a rule for that, and that rule is "(while doing an assigment) current goes from + of voltage source to - of voltage source.

Following that rule, I did this:

And from that I wrote these 3 equations:

I2 = I1 + I 3

U1 + U2 + U3 = I1*(R1 + R2 + R3) + I2*R4

U4 + U3 = I3*(R5 + R6) + I2*R4

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I2 = I1 + I 3

86 = 24*I1 + 20*I2

86 = 36*I3 + 20*I2

Did I do everything right here ? Because I got that I2 = -1.654 A

Did I do something wrong with equations or is my math just bad ?