Cramer's rule tells you that the value of x in the system of equations
[tex]ax+by=c\\dx+ey=f[/tex]
is given by
[tex]x=\dfrac{ce-fb}{ae-bd}[/tex]
For your equations, this evaluates to
[tex]x=\dfrac{16\cdot 1-8\cdot 3}{1\cdot 1-3\cdot 3}=\dfrac{-8}{-8}\\\\x=1[/tex]
