In the Manhattan SC book, page 87 , it is mentioned that

The employees were upset by their low pay, poor working conditions , and limited creative outlets


i feel that we need to repeat the preposition 'By" for each part and the correct sentence could be

The employees were upset by their low pay, by poor working conditions , and by limited creative outlets

The stem here is "The employees were upset "

Tutors , pls comment

Query2 --

While working on questions in page 91

Many teachers have chosen to seek employment in the suburbs rather than face low salaries in the city

In my opinion , it shd be

Many teachers have chosen to seek employment in the suburbs rather than TO face low salaries in the city

Tutors,

I am getting confused day by day seeing such questions and completely confused when to repeat the preposition after the Conjunction . Please help...
[b[/b]

always remember that we don't make the rules; we're just a mouthpiece for the rules that the gmat test writers choose to follow.
one of those rules is the idea that it's ok to omit 'to' from infinitives after #1 in a series. (for a problem that is closely related to this one, see #40 in the purple og11 verbal supplement. DO NOT post any specifics related to that question here.)

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in general, here's the rule to follow with omitting helping words such as 'to':
if you need to repeat the word to prevent some sort of ambiguity, repeat it.
if the parts of the parallel construction are obnoxiously long, to the point where the parallel construction itself would be difficult to discern WITHOUT the repeated helping word, repeat the word.
otherwise, don't repeat the word (in the name of concision).