I think you mean:
-2x-8y=-42, -4x+6y=-18.
Both equations can be reduced:
2x+8y=42, -2x+3y=-9.
Add the equations: 11y=33, y=33/11=3.
Now substitute y=3 in either equation:
-2x+9=-9, 18=2x, so x=18/2=9.
CHECK
-2x-8y=-18-24=-42 OK; -4x+6y=-36+18=-18 OK.
SOLUTION: x=9, y=3.