-4x-2y = 16
2y = -4x-16
Get one variable alone on both equations
-4x - 16 = 2y
-4x - 16 = 2y
You'll realize that they're the same equation.
Use substitution
-4x-16 = -4x-16
0 = 0
x = all solutions
Use x = all solutions in an earlier equation to find y
-4x - 16 = 2y
SInce x can be all solutions y is also all solutions
y = all solutions