The question asks the price of one DVD without tax.
Otherwise the information given on the included tax which is said to be 7% would be irrelevant. Support to this is that when you calculate the price before tax (66,34 : 1,07) you get a real number = 62 which is again divisible by 5 DVD's = 12,5

Thanks Bronson!

HELP:
A consumer electronics company sells 6.7 million MP3 players per month at a price of $100 apiece; when the price is lowered to $80, the company sells 10.2 million players per month. How many MP3 players can the company expect to sell per month at a price of $75?

QualityOfLife wrote:HELP:
A consumer electronics company sells 6.7 million MP3 players per month at a price of $100 apiece; when the price is lowered to $80, the company sells 10.2 million players per month. How many MP3 players can the company expect to sell per month at a price of $75?

Where is this question from?

That's not a GMAT style question for two reasons.

First, we're not usually tested with such big numbers and the only way to solve this would be to plot the graph.

Second, we're not actually told that supply/demand is linear (S/D isn't linear for all products) and we can't assume that it is, so we don't have enough information to answer the question. We're not expected to be economics experts on test day.