Official Guide Explanation:
Problem Solving #165




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Solution and Metadata

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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