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What is the value of x?

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What is the value of x?

by AAPL » Fri Nov 17, 2017 11:39 am

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What is the value of x?

(1) 5x + 3y = 15
(2) y = 5 - (5/3)x

The OA is E.

Please, can any expert assist me with this DS question? I don't have it clear and I appreciate if any explain it for me. Thanks.
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Source: — Data Sufficiency |

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by [email protected] » Fri Nov 17, 2017 11:48 am

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Hi AAPL,

We're asked for the value of X.

1) 5X + 3Y = 15

Fact 1 gives us just 1 equation to work with. Since there are no 'limitations' on the value of X or Y, X could be anything (positive, negative, 0, a fraction, etc.).
Fact 1 is INSUFFICIENT

2) Y = 5 - (5/3)X

Fact 2 also gives us just 1 equation to work with. Since there are no 'limitations' on the value of X or Y, X could be anything (positive, negative, 0, a fraction, etc.).

Since this equation is somewhat 'odd-looking', I'm going to re-write it here:
Y = 5 - (5/3)X
Y + (5/3)X = 5
3Y + 5X = 15
5X + 3Y = 15
Notice how this is the exact SAME equation that we were given in Fact 1...
Fact 2 is INSUFFICIENT

Combined, we still have just 1 equation (NOT 2 different equations), so X can still be any value.
Combined, INSUFFICIENT

Final Answer: E

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
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