In addition to your standard English and math courses (including Algebra), you could take bookkeeping, statistics and any other business courses offered.
It is the total amount of time in days that a vendor will allow the purchaser of received goods or services to make payment, usually before any interest is due.
It would not be an expense. It would be a line item on the balance sheet, not sure which line item it would fall under.
As an offset to the capital