5x-4y=10 2x+8y=4

rewrite #1 and you get

10x-8y=20
2x+8y=4

Now add the two equations and y goes away. Solve for x, then get y.

Thanks Steve.

But how???

Please explain it.

If you add the two equations, you get

12x = 24

because -8y+8y = 0

Now you know x=2, so y=0