50,000 x .7 x .02 = 700  This is the amount of collections forfeited due to taking the discount.

50,000 - 700 = 49,300  This is the net collections.

nacol wrote: Why can't these review programs make it this simple?

Because nearly everyone who graduated high school after 1985 learned how to punch calculator buttons instead of learning quick shortcuts for mental math.

Working the problem forwards, like the BISK explanation does, shows you the steps clearly in a way everyone can follow.  It's sometimes slow and tedious, but how you get there is always easy to see.

Working the problem backwards, like I did, comes from getting comfortable with fast mental math.  Example: Quick! Multiply $4.89 times three!  Fast mental math method: $4.89 is .11 less than $5.00, so multiply $5.00 times three ($15.00) and subtract .33.  Answer: $14.67.

Unfortunately, I can't help you with Wiley's explanation because I only bought the Wiley REG book.