Set up the following chemical balance equation as a system of linear constraints in order to find the coefficients {xi}1i4 via Gauss-Jordan

Set up the following chemical balance equation as a system of linear constraints in order to find the coefficients {xi}1≤i≤4 via Gauss-Jordan elimination

x1NaOH+x2H2SO4 →x3Na2SO4 +x4H2O

I need step by step solution. 

what i have so far is...starting matrix-->

1 0 -2 0

1 4 -4 -1

1 2 0 -2

0 1 -1 0

and then...

x1=2x3

x1+4x2=4x3+x4

x1+2x2=2x4

x2=x3

Please help. Thank you.