Hi, this is my first time posting and am not sure if I am doing this right, however, I am finding this difficult to understand:

(1 -2 k)

(2 1 2) = A

(3 2 1)

(-5 -2+2k -4-k )

(8 -1-3k -2+2k) = B

(1 -8 5 )

(k-n 0 0)

(0 k-n 0) = AB

(0 0 k-n)

x-2y+z=1

2x+y+2z=12

3x+2y-z=3

I know that I need to find the inverse of A however I am not used to doing this with 3*3 matrices (we haven't been taught a rule for this), what we were told was that there is a connection with 'I'. I only really need help finding the inverse of A.

Thank you so much for your help in advance, I really appreciate any time you spend on this!