The purpose of this study is to show the diverse nature of the objects we call "equations", "polynomials" and "unknowns". Beneath these universalizing titles and the application of modern mathematical language are hidden particular mathematical practices, specific modes of reasoning and different strategic objectives. In order to underline this diversity, this study focuses on two medieval treatises: the Yigu yanduan written by Li Ye in 13th century China and the Bījagaṇitavātamsa written by Nārāyana in 14th century India. Both treatises deal with the construction of equations. My approach is based on literal translations and analyses of the texts, following techniques borrowed from philology. I tackle the texts through their structures. This results in several hypotheses.
