This is as close as I could come:
{
[ -x_1, , , , ,+,x_4,=,\qquad 130],
[ , , , ,x_3,-,x_4,=,\qquad\quad 60],
[ , ,x_2,-,x_3, , ,=,-240],
[\qquad x_1,-,x_2, , , , ,=,\qquad\quad 50]
:}
The spacing is a bit ad hoc, but perhaps it is good enough for you.