Double the second equation (multiply by 2)...
2(x-2y=10)
2x-4y=20
Bring in the second equation and add the equations:
(2x-4y=20)
+ (5x+4y=8)
7x=28
x=4
Plug in x into one of the equations to get y...
(4)-2y=10
-2y=6
y=-3
(6,-3)
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