Other chapters of his book discuss the alloying of money, the barter of commercial things, and companies made among parties, though it is better known for discussions of the "finding of square and cube roots" and the "multiplication of whole numbers."  
In the 13th chapter of this man's most famous book, we encounter the problems of the "four men who found a purse," the "five men who bought a horse," and a tree which lies partly underground.  Those problems can be solved with the method "elchataym," which is also known as the method of double false position.  Other chapters of his book discuss the alloying of money, the barter of commercial things, and companies made among parties, though it is better known for discussions of the "finding of square and cube roots" and the "multiplication of whole numbers."  In the first chapter of his book, he explains how to use the "nine Indian figures" to write all numbers.  This businessman (*) from Bugia wrote The Book of Squares, but his major work was a 1202 book that introduced algebra to Italy.  FTP, name this author of the Liber Abaci, a mathematician best known for a namesake sequence which begins with the numbers 1, 1, and 2.
In the 13th chapter of this man's most famous book, we encounter the problems of the "four men who found a purse," the "five men who bought a horse," and a tree which lies partly underground.  
Leonardo Pisano or Fibonacci (prompt on Liber Abaci or the Book of Calculation if someone is confused and says it prior to the asterisk)