Write the augmented matrix, and then solve the system, using Gauss Jordan elimination on the

augmented matrix.
x + 2y - z = 4
-2x + y - 4z = -6
4x - 3y + 2z = -10

1 answer

lots of writing...
Here is a neat page
http://www.gregthatcher.com/Mathematics/GaussJordan.aspx

tell it you have 3 rows and 4 columns, then enter the values

Notice it takes it all the way to the matrix
1 0 0 ?
0 1 0 ?
0 0 1 ?

you only have to go as far as
1 x x x
0 1 x x
0 0 1 x

get the answer from the last row, sub that back into the second, and finally into the first.