start clearing the x in the first equation
[tex]\begin{gathered} 4x=-1+8y \\ x=-\frac{1}{4}+2y \end{gathered}[/tex]insert this equation into the second one
[tex]\begin{gathered} 7\cdot(-\frac{1}{4}+2y)-14y=4 \\ -\frac{7}{4}+14y-14y=4 \\ -\frac{7}{4}\ne4 \end{gathered}[/tex]the system has no solution
