Edit: Sorry, I figured this out shortly after posting. It's a simple problem but I hadn't used matrix equations before. 1. The problem statement, all variables and given/known data If A, B, and C are all square matrices of the same size, show that AB commutes with C if A and B both commute with C. 2. Relevant equations Formula for matrix multiplication 3. The attempt at a solution All I know is AC = CA BC = CB A, B, and C are square matrices of the same size I want to prove that (AB)(C) = (C)(AB). But I am not sure how to do this, or even how to get started.