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What is the value of 2x-y?

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by Max@Math Revolution » Fri Sep 13, 2019 6:37 am

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[GMAT math practice question]

What is the value of 2x-y?

1) |3x-2y+4| + |-x+2y-2|=0
2) x and y are rational numbers
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Source: — Data Sufficiency |

by Max@Math Revolution » Sun Sep 15, 2019 5:36 pm
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Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.
Visit https://www.mathrevolution.com/gmat/lesson for details.

The first step of the VA (Variable Approach) method is to modify the original condition and the question. We then recheck the question. We should simplify conditions if necessary.

Condition 1) is equivalent to two equations: 3x-2y+4=0 and -x+2y-2 = 0. When we solve this system of occasions, we obtain x = -1 and y = 1/2. Thus, condition 1) is sufficient on its own.
Note the VA tells us this will be the case. The question has two variables, but condition 1) provides 2 equations.

Condition 2) is clearly not sufficient on its own.

Therefore, the answer is A.
Answer: A
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