the first thing to notice in this problem is the presence of the expressions (a - b) and (b - a).
(a - b) and (b - a) are opposites. therefore, exactly one of them is positive, and the other is negative.
this is the sort of thing you should notice right away, and should "take away" from this problem and store in your head for future use.
given this fact, the only way for this inequality to work is if (a - b) is negative and (b - a) is positive.
therefore:
REPHRASED QUESTION:
is b - a > 0?
FURTHER REPHRASE:
is b > a ?
once you have this rephrase, the sufficiency of #1 is trivial.
to show that #2 is insufficient, note that |a - b| is a symmetric expression; i.e., it's the same as |b - a| (each of these is "the distance between a and b"). given that symmetry, there's no way that this expression could determine which of the two is greater.
thus (a)
Ron has been teaching various standardized tests for 20 years.
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Pueden hacerle preguntas a Ron en castellano
Potete chiedere domande a Ron in italiano
On peut poser des questions à Ron en français
Voit esittää kysymyksiä Ron:lle myös suomeksi
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Quand on se sent bien dans un vêtement, tout peut arriver. Un bon vêtement, c'est un passeport pour le bonheur.
Yves Saint-Laurent
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