I am having a lot of trouble solving systems of equations by putting them in RREF.

I don't understand how you know what to do after each step. I keep working the same problem and I'm not getting anywhere.

The system is :

2x + y + 3z = 0

y + 3z = 5

x + 3/2y + 9/2z = 5

which would make my augmented matrix:

2 1 3 :0

0 1 3 :5

1 3/2 9/2 :5

I've started it in so many ways, but then I go through steps and can't get anywhere.

Can someone please demonstrate a step-by-step way of getting this in RREF and if possible give some tips that explain the best way to do this? Thanks