Official Guide Explanation:
Problem Solving #140

Background

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Solution and Metadata

Question: 140
Page: 172
Difficulty: 4 (Moderately Easy)
Category 1: Algebra > Linear Equations-Two Unk >
Category 2: Word Problems > Other >

Explanation: Like so many GMAT word problems, this one gives you two equations. If f is the weight of his first lift and s is the weight of his second, f + s = 750, and 2f = s + 300. Rearrange the first equation so that it can be substituted: s = 750 - f. Then substitute into the second equation:

2f = (750 - f) + 300

2f = 1050 - f

3f = 1050

f = 350, choice (D).

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