Jordanus de Nemore's De Numeris Datis stands as a groundbreaking text, marking the advent of advanced algebra in Western Europe. Written in the 13th century, the work assumes mastery of basic algebra and progresses to develop a systematic approach to quadratic, simultaneous, and proportional equations, many of which had not been previously articulated in European mathematics. By providing sophisticated techniques for numerical analysis, Jordanus not only addressed the needs of his contemporary mathematical community but also laid a foundational stone for the algebraic advancements that followed. The text bridges a gap between the classical mathematical traditions of the Greeks and the revolutionary algebraic methods emerging in the medieval Islamic world, showcasing Jordanus’s role as an intellectual conduit in a period of vibrant cross-cultural exchange. Despite scant biographical information about Jordanus himself, his contributions resonate through the depth and structure of his work. De Numeris Datis combines theoretical rigor with practical application, offering propositions and methods that are both abstract and directly applicable to real-world problems. The text's influence is underscored by its enduring presence in medieval and Renaissance scholarship, with numerous surviving manuscripts and commentaries attesting to its relevance. By formalizing algebraic analysis in a way that prefigures later works like Viète's Introduction to the Analytical Art, Jordanus elevated algebra from a computational tool to a discipline of logical inquiry, cementing his legacy as one of the seminal figures in the history of mathematics. This title is part of UC Press's Voices Revived program, which commemorates University of California Press’s mission to seek out and cultivate the brightest minds and give them voice, reach, and impact. Drawing on a backlist dating to 1893, Voices Revived makes high-quality, peer-reviewed scholarship accessible once again using print-on-demand technology. This title was originally published in 1981.