I cant remember this would be substitution, correct? If so,
2x+8y=4
-2x -2x
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8y=4-2x
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8 8 8
y=1/2-1/4x
substitute this into 2x+4y=20
2x+4(1/2-1/4x)=20
2x+2-x=20
-2 -2
---- ----
2x-x=18
1x=18
x=18
substitute x in the equation
2(18)+8y=4
36 + 8y=4
-36 -36
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8y=-32
---- ------
8 8
y= -4
x= 18