Question

What is -4x-2y=-12+4x+8y=-24 by elimination

Answer 1

I think you have an extra plus sign.

-4x -  2y = -12
 4x + 8y = -24

Add the equations to eliminate x.

6y = -36

y = -6

Now multiply the first equation by 4 and add to the second equation.

-16x - 8y = -48
  4x + 8y = -24
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-12x        = -72

x = 6

Solution: x = 6 and y = -6

Answer 2

Since the 4x and -4x cancel out, this is what you get:
6y=-36