Official Guide Explanation:
Data Sufficiency #7

Background

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Solution and Metadata

Question: 7
Page: 153
Difficulty: 4 (Moderately Easy)
Category 1: Algebra > Linear Equations-Two Unk >

Explanation: Statement (1) is not sufficient. We don't know how many salespeople there are; if we call the number of salespeople s and the number of cars to be sold c, we can come up with the equation:

c = 4s + 23

Without the value of s, we can't find the value of c.

Statement (2) is also insufficient. It gives us a similar equation:

c = 6s + 5

Again, two variables is too much to handle with one equation.

Taken together, the statements are sufficient. We have two linear equations with two variables--enough to solve for the value of c. Choice (C) is correct.

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