Hi gmat_guy666,

This DS question, while a little "wordy" in spots, is really more about your organizational skills than your math skills.

We're asked what FRACTION of the 32 million union members PAID 80% OR LESS of their annual union dues during a certain year.

Fact 1: 37.5% of the union members left 19% OR LESS of their union dues UNPAID.

Saying that "37.5% left 19% OR LESS unpaid" means the same as saying "37.5% paid 81% OR MORE of their dues".

By extension, the other 62.5% paid LESS THAN 81%, but that's NOT what the question asked for (the question asked for the fraction that paid 80% or LESS). There is a small group of people - the 1% between 80% and 81% - that we don't know enough about. The size of that group will affect the answer to the question.
Fact 1 is INSUFFICIENT

Fact 2: The ratio who pads 80% OR LESS to the members who paid MORE THAN 80% is 3:5

This Fact defines the exact 2 groups that we need to know about. The ratio of 3:5 means that 3/8 of the employees paid 80% OR LESS and 5/8 of the employees paid MORE THAN 80%. This information answers the question.
Fact 2 is SUFFICIENT.

Final Answer: B

GMAT assassins aren't born, they're made,
Rich