we have the following:
[tex]\begin{gathered} 3x+4y=50 \\ -2x=y \end{gathered}[/tex]replacing:
[tex]\begin{gathered} 3x+4\cdot-2x=50 \\ 3x-8x=50 \\ -5x=50 \\ x=-\frac{50}{5} \\ x=-10 \end{gathered}[/tex]now, from y:
[tex]\begin{gathered} y=-2\cdot-10 \\ y=20 \end{gathered}[/tex]Therefore:
x = -10
y = 20
