Solve the system by addition.
2x-4y=7
4x+2y-1
2x-4y=7
4x+2y-1(I guess that's = 1 and not -1?)
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multiply equation 2 by 2 to obtain
8x+4y=2
then add equation 1. Can you procedd now? The y term cancels, leaving just the x term and a number. Solve for x first.