If you use FOIL to multiply these two brackets, it will lead you what is exactly written (xa+xb+ya+yb)
so it is correct
A
So 400,000 DVD sales with a 31% decline means in the 1st year following, there will be a decline of 124,000 DVDs sold. So we need to take 400,000 - 124,000, which equals a starting point for year two is 276,000 DVDs.
So a 31% decline on 276,000 = 85,560. So we need to subtract that from 85,560 from 276,000 which is 190,440. So at the end of the second year, DVD sales were only 190,440. That's also out starting point of the 3rd year.
So 31% of 190,440 equals 59,036.4 for the third year of DVD sales. So we need to subtract 59,036.4 from out third year starting point of 190,440, which equals 131,403.6, but since you can't have parts of DVDs, we'll round the decimal point fraction to a whole number to end up with 131,404 DVDs sold in year three.
So after three years of a 31% yearly decline in DVD sales you end up with DVD sales are 131,404
Any number inside the modulus sign becomes positive. This means 
and so we have,
Solving these gives us
However if we check the second solution in the original equation we obtain 
. This is false and so 
can't be a solution.
Therefore the only solution is 
.
(Note: I'm not sure why the second solution didn't work but when there's a modulus sign involved it always pays to check your final answers to be sure. I'll have a think about it but in case you find out before I do, I'd be interested to know in the comments.)
There really isn’t a possible answer since there is not enough information given. Not from what I have learned so far at least, but using common sense, and the process of elimination I would say 30
