Please help me. I have no idea how to solve this problem. How do I even start?

x+y+z=5

2x+3y+5z=8

4x+5z+2

1 1 1 5

2 3 5 8

4 0 5 2

1 1 1 5

0 1 3 -2

4 0 5 2

1 1 1 5

0 1 3 -2

0 -4 1 -18

1 1 1 5

0 1 3 -2

0 0 13 -26

plus there are arrows connecting the rows of numbers together. what's that all about?