Question

Matrices A and B are shown below.

Answer 1

The first thing you must remember is that the product of matrices is done by multiplying rows by columns.
 For this case, the AB matrix is
 AB = [1 0 0; 0 1 0; (x + 1) 0 y]
 Equalizing the identity matrix we have
 AB = I
 [1 0 0; 0 1 0; (x + 1) 0 y] = [1 0 0; 0 1 0; 0 0 1]
 Therefore we have
 x + 1 = 0
 y = 1
 The values of x and y are
 x = -1
 y = 1 
the answer is 
 X=-1
 Y=1