Proportions and Algebra in Mathematical Treatment of the Middle Ages and the Renaissance

The purpose of this work is to highlight the connection between algebra and the proportions in various issues taken from about thirty manuscripts and printed works by various authors, in a time span ranging from the thirteenth century to the early seventeenth century. The examined works are either placed in the context of the abacus treatises or more specifically meaningful and fundamental for the development of algebra. Within a wide range of cases, the problems were selected by considering their historical relevance, interest and originality, both in their contents and terms, in order to obtain an exemplifying survey that does not want to be exhaustive, but provides a general overview, giving suggestions for further study.