A stretchy tree is here marked with bold edges:
Then I get the the system of equations here by matrix: A=\begin{pmatrix} 0 & 0 & 0 & 1\\ -1 & -1 & 0 & 0\\ 1 & 0 & 0 & 0\\ 0 & 0 & -1 & 0 \ \end{pmatrix} and
-b=\begin{pmatrix} 2\\ -8\\ 5\\ -6 \ \end{pmatrix}
A is with the rows a, b, c, d and the columns (b, c), (b, e), (d, e), (e, a).
I have to solve the system Ax=-b
So I think I got : $A^{-1}$=\begin{pmatrix} 0 & 0 & 1 & 0\\ 0 & -1 & -1 & 0\\ 0 & 0 & 0 & -1\\ 1 & 0 & 0 & 0 \ \end{pmatrix} And then the solution $A^{-1}(-b)$=\begin{pmatrix} 5\\ 3\\ 6\\ 2 \ \end{pmatrix} so $x_{bc}=5$,$x_{be}=3$, $x_{de}=6$,$x_{ea}=2$.
Is that correct or am I totally wrong?