What are some of the challenges one might experienced using matrix operations?

The main one in my experience is typing the matrix correctly into the calculator.

Computations using large matrices require a lot of CPU time.

what does CPU mean

CPU stands for Central Processing Unit. It is the main component of a computer system that performs most of the processing inside the computer. The CPU interprets and executes instructions, performs calculations, and manages data flow between different parts of the computer system. It is considered the brain of the computer.