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## Official Guide Explanation:Problem Solving #165

Background

This is just one of hundreds of free explanations I've created to the quantitative questions in The Official Guide for GMAT Review (12th ed.). Click the links on the question number, difficulty level, and categories to find explanations for other problems.

These are the same explanations that are featured in my "Guides to the Official Guide" PDF booklets. However, because of the limitations of HTML and cross-browser compatibility, some mathematical concepts, such as fractions and roots, do not display as clearly online.

Question: 165
Page: 176
Difficulty: 5 (Moderate)
Category 1: Algebra > Linear Equations-Two Unk >
Category 2: Word Problems > Other >

Explanation: This is trickier than the run - of - the - mill GMAT question with two equations, but it can be solved the same way. If Lois has x more dollars than Jim has, we can set up the equation: l = j + x. If they have a total of y dollars, there's another equation: l + j = y. Since we know that the l's will eventually disappear (we're looking for Jim's number of dollars, and x and y are the only variables in the answer choices), set the second equation equal to l: l = y - j, then set the two equations equal to each other: j + x = y - j. Then simplify:

2j = y - x

j = ((y - x)/2), choice (A).

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