The system has no solution.

The system has a unique solution:

System A

$-x-4y=-8$

$x+4y=8$

$-x-4y=-8$

$x+4y=8$

The system has infinitely many solutions.

They must satisfy the following equation:

$y=$

The system has no solution.

The system has a unique solution:

$(x,y)=$

$x+3y=9$

$-x-3y=9$

System B

$x+3y=9$

$-x-3y=9$