I strongly encourage you to figure how to get
your calculator to perform matrix multiplication
and inversion, if you haven't already. You might
start by reproducing today's computations.

You can verify today's matrix computations
using the following sequence of commands
at live.sympy.org:

a=Matrix([[1,3],[2,4]])

ai=a.inv()

ai

h=Matrix([[1,0],[-1,1],[0,5]])

b=Matrix([[1,1,1],[0,1,1],[0,0,1]])

b*h*ai

Also into live.sympy.org, you can copy, paste,
and modify the commands from my IPython
computations posted on the course website.