Book excerpt: Within the field of mathematics teacher (PST) education, a profound challenge echoes—the persistent gap between theoretical understanding and practical application. This lingering divide raises a critical concern, one that finds its focus in the exploration of transformative tools known as approximations of practice. These tools aim to provide a realistic and contextualized environment for PSTs to cultivate their teaching skills. However, the broader, often overlooked issue permeating this educational terrain is the question of equity in mathematics instruction—an issue that this book endeavors to unravel and reshape, positioning equity at the forefront of pedagogical considerations. Promoting Equity in Approximations of Practice for Mathematics Teachers, a compelling work that not only delves into the transformative role of approximations but also champions equity as a cornerstone in reshaping the landscape of mathematics education. This groundbreaking work has a dual objective—firstly, to furnish mathematics teacher educators and researchers with a comprehensive overview of the current landscape of approximations in mathematics education. It moves beyond a mere survey, encouraging readers to critically analyze frameworks and design choices that either foreground or dismiss equity in these pedagogical spaces. Divided into three sections, the book delves into the spectrum of work characterizing approximations in mathematics teacher education. The first section surveys diverse approaches, acknowledging the current lack of focus on equity. The second section critically examines the intersection of equity and approximations, fostering collaborations between experts in mathematics education and equity-focused researchers. The third section takes a forward-looking stance, envisioning the future of equity-focused approximations in mathematics education.