(1) -5a-2b+4c=11
(2) 4a+5b-3c=-26
(3) a+5b-3c=-23
(2)-(3)=3a=-3, a=-1
(1) becomes 5-2b+4c=11, -2b+4c=6 (4)
(2) becomes -4+5b-3c=-26, 5b-3c=-22 (5)
5(4)+2(5)=-10b+20c+10b-6c=30-44=-14, 14c=-14, c=-1.
Substituting for c in (4): -2b-4=6, -2b=10, b=-5.
SOLUTION: a=c=-1, b=-5.