During my PhD, I have demonstrated for a number of undergraduate courses.
MT2000 Python Workshop
An introductory course to programming, taught in Python. I was an assistant demonstrator, helping students with any problems they had.
MT2504 Combinatorics and Probability Computing Project
Students taking MT2504 were required to complete a project on combinatorics in Python; I was an assistant demonstrator and marked half of the solutions.
MT2505 Abstract Algebra
Students taking MT2505 were required to complete a significant project on combinatorics in Python; I was an assistant demonstrator and marker, and also wrote an automated test suite to help mark the solutions.
I assisted at a drop-in session for undergraduates with questions about any sub-honours mathematics modules.