Final answer:
The book Al-Jabr, which became the basis for modern-day algebra, was created by the Arabs, specifically by scholars like Al-Khwarizmi.
Step-by-step explanation:
The group of people who created the book Al-Jabr, which became the basis for modern-day algebra, are the Arabs. Arab scholars like Al-Khwarizmi, who lived from 780-850, were instrumental in the development of algebra. Al-Khwarizmi's book, "The Compendious Book on Calculation by Completion and Balancing," published around 820, is considered one of the foundational works of algebra.