Step-by-step explanation:
[tex]2x-y=5\\-y=5-2x\\-y=-2x+5\\\frac{-y}{-1} =\frac{-2x}{-1} +\frac{5}{-1} \\y=2x-5[/tex]
[tex]x+2y=-1\\2y=-1-x\\2y=-x-1\\y=\frac{-x-1}{2} \\y=-\frac{x}{2}-\frac{1}{2}[/tex]
[tex]x-y=7\\-y=7-x\\\frac{-y}{-1} =\frac{7}{-1} -\frac{x}{-1} \\y=-7+x\\y=x-7[/tex]
