Online learning environments are being used for teaching and learning of mathematics at university level. Exploiting the potential of digital technology, these Internet-based environments administer computer-generated homework, assistance and feedback for students. This article presents a case-study of a small group of ?undergraduate engineering students' learning activity in mathematics in an online environment. The study focuses on students' interactions with the online environment to make sense of the affordances of this environment. Utilizing multiple sources of data aid in analyzing the intentional and the operational aspects of students' interactions with several resources in this environment. With regard to both of these aspects, the affordances are thus viewed as features of the environment which support students' engagement with the mathematical tasks. The analyses show that the students incorporated several online resources for solving the tasks posed in the automated system. Students met requirements of final answers in the automated system through varying sequences of mathematical operations for the posed tasks. The conditions of the automated system as well as the rules of the collective activity system played a role in students' interactions with the mathematical tasks.