A-->
r3+r1
1 7 2 8
0 -5 3 6
0 0 5 15
r3*(1/5),r1-2r3,r2-3r3
1 7 0 2
0 -5 0 -3
0 0 1 3
r2*(-1/5),r1-7r2
1 0 0 -11/5
0 1 0 3/5
0 0 1 3
A-->
r3+r1
1 7 2 8
0 -5 3 6
0 0 5 15
r3*(1/5),r1-2r3,r2-3r3
1 7 0 2
0 -5 0 -3
0 0 1 3
r2*(-1/5),r1-7r2
1 0 0 -11/5
0 1 0 3/5
0 0 1 3