1MS : 2.5.21 j

[1,  1, 1,  25]
[1, -1, 1,   5]
[1, -2, 2, -10]

L_2 <- L_2 - 1 * L_1

[1,  1, 1,  25]
[0, -2, 0, -20]
[1, -2, 2, -10]

L_3 <- L_3 - 1 * L_1

[1,  1, 1,  25]
[0, -2, 0, -20]
[0, -3, 1, -35]

L_2 <- -1/2 * L_2

[1,  1, 1,  25]
[0,  1, 0,  10]
[0, -3, 1, -35]

L_3 <- L_3 + 3 * L_2

[1, 1, 1, 25]
[0, 1, 0, 10]
[0, 0, 1, -5]