Official Guide Explanation:
Data Sufficiency #56

Background

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Solution and Metadata

Question: 56
Page: 277
Difficulty: 4 (Moderately Easy)
Category 1: Geometry > Triangles > other
Category 2: Algebra > Linear Equations-Two Unk >

Explanation: The angles in a triangle add up to a total of 180 degrees, so in this question, x + y + z = 180. Since we're looking for the value of z, we can set that equal to z: z = 180 - (x + y). Statement (1) is sufficient: given the sum of x and y, we can subtract it from 180 and find z. Statement (2) looks similar, but is insufficient. We could use it to solve for x, but not for z.

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