If 3x − y = 11, what is the value of x?
(1) y = 4
(2) x + y = 9
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Data InsightsData Sufficiency
Free GMAT Data Sufficiency Practice Question
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Answer & Explanation
Correct answer
D
The stem gives one equation, 3x − y = 11, in two unknowns; we want x. Each statement supplies a second, independent equation.
Statement (1): y = 4 substituted into the stem gives 3x − 4 = 11, so 3x = 15 and x = 5. A single value. Sufficient.
Statement (2): x + y = 9 combined with the stem 3x − y = 11: adding the two equations gives 4x = 20, so x = 5. A single value. Sufficient.
The (C) trap pairs the statements, forgetting that the stem already provides one equation, so each statement is the second equation that completes a solvable system on its own. The (A)/(B) trap arbitrarily privileges one statement when each independently pins x.