Luca Pacioli: Luca Pacioli was an Italian mathematician, friar (a religious man in the twelve to thirteenth century)  born in Sansepolcro in The Republic Of Florence, Italy. He was known for the inventing  book-keeping and also collaborating with Leonardo Da Vinci on art.

Leonardo Da Vinci: Leonardo Da Vinci was born in Vinci, Italy (Da Vinci means From Vinci) and was the son of a Government official.  He had 12 siblings and his dad was married to 4 woman during his life.  The first two died young and the first mother 7 children and the other had 6.  Leonardo was a gifted child, but he could not focus.  He was good at painting, sculpting, and drawing.  He was famous for his painting The Mona Lisa and The Last Supper.

Mariners Astrolabe:  It was invented by the Portuguese in 1481.  The mariners astrolabe  was also called the sea astrolabe.  The mariners astrolabe improved sea travel and navigation, which led to the age of discovery that lasted 300 years!   The Pope gave Portugal and Spain the monopoly on any new and undiscovered lands. The mariners astrolabe was better than a land astrolabe because it was built to work well at sea.

Double-Entry Booking Keeping: Double Entry Book Keeping is a system of book-keeping.  It efficiently shows financial transactions by using two columns for each accounting entry.  There is a credit column which shows positive cash flow, or money in.  There is also a debit column which shows negative or outgoing cash flow, also known as debt.  For example; A person buys a house for $100,000 and to pay for it they pay $40,000 cash and borrow $60,000.  He has $100,000 in assets, $60,000 in liabilities and $40,000 in equity.