x+[2 1 8] =[6 -1 8] [4 3 0] [-5 2 -7]
[2 1 8] [4 3 0]
x =[6 -1 8]-[2 1 8] [-5 2 -7][4 3 0]
x =[6-2 -1-1 8-8] [-5-4 2-3 -7-0]
x =[4 -2 0] [-9 -1 -7]