This GitHub repository contains two folders: Slides and Paper. These folders contain the presentation slides and a summary paper respectively, both related to the topic of X-ray CT and the basic mathematics needed for it. This work is based on the first three chapters of the book Computed Tomography: Algorithms, Insight, and Just Enough Theory by Per Christian Hansen, Jakob Sauer Jorgensen, and William R.B. Lionheart and was done for the purpose of the seminar: Computational Methods for X-ray Computed Tomography (see: https://ciip.in.tum.de/teaching/cm-xct_ss23.html)