I have a matrix

1 0 5 0 0

0 1 1 5 0

0 0 0 0 1

Which gives the three equations:

X1 + 5X3 = 0

X2 + X3 + 5X4 = 0

4X5 = 0

Now in my notes it says that you can solve it to get:

X1 = 2X3 + 0X4

X2 = 6X3 + 2X4

X3 = 1X3 + 0X4

X4 = 0X3 + 1X4

X5 = 0X3 + 0X4

Could someone help explain to me how you go from the first equations to the second, for the life of me i can't figure it out