Lol, sorry but what is !!!!det A!!! not yet learned
and how to know that the inverse in not possible, i mean you might think there may be an answer to the matrix and continue solving it with various numbers, So any better ways
When you learn about the determinant you will get a method for testing whether the inverse of a given matrix exists. I have already given the general apporach for finding the inverse of a matrix. You can use moo's for a 3x3, if the order is higher you're stuck with with what I've already told you.
It sounds like it might be better if you wait until you've been taught more regarding this subject.