Please give step by step instructions and name each step like triangular form, augmented matrix etc so I know when and what to do and can understand it. We are not using calculator so the steps need to be shown to the solution.

1) Solve the system using elementary row operations on the equations of the augmented matrix. Follow the systematic elimination proceedure.

xsub1 +5xsub2 = 7
-2xsub1 - 7xsub2 = -5

2) Find the point of intesection of the lines xsub1 - 5xsub2 =1 and 3xsub1 - 7xsub2 = 5

3) What is a row operation in matrices? What you do to transform it from the augmented matrix to the triangular form where you have a row of ones and 0's under and above the leading ones?

4) Solve the system.

xsub2 + 4xsub3 = -5
xsub1 + 3xsub2 +5xsub3 = -2
3xsub1 + 7xsub2 + 7xsub3 = 6