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Source: — Data Sufficiency |
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by GMATQuantCoach » Sun Jul 12, 2009 3:52 pm
(1) 2x-2y=1
2(x - y) = 1
x - y = 1/2
x = 1/2 + y

choose y = 1, then x = 3/2
choose y = -1, then x = -1/2

Insufficient

(2) x/y > 1
x/y - 1 > 0
(x-y)/y > 0

choose x = 2, y = 1
choose x = -2, y = -1

Insufficient.

When combined.
x - y = 1/2
(x-y)/y > 0

Replace x - y with 1/2
1/(2y) > 0
Then y >0
x = 1/2 + y > 0

Both x > 0 and y > 0.

The answer is C.
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