A hasn't been shown in the matrix operation, therefore we need to consider all the possibilities for A and all operations.
Let matrix X=
⎛ 1 3 2 ⎞
⎜ 2 1 1 ⎟
⎝ 4 0 3 ⎠
Let matrix Y=
⎛ 7 1 3 ⎞
⎜ 1 0 3 ⎟
⎝ -1 -3 7⎠
ADDITION/SUBTRACTION
X+A=Y, A+X=Y, X=Y-A: A=
⎛ 6 -2 1 ⎞
⎜ -1 -1 2 ⎟
⎝ -5 -3 4 ⎠
X-A=Y, X=A+Y, X=Y+A: A=
⎛ -6 2 -1 ⎞
⎜ 1 1 -2 ⎟
⎝ 5 3 -4 ⎠
MULTIPLICATION
First determine X-1 and Y-1.
|X|=-11, |Y|=44.
X-1=
⎛ 3 -9 1 ⎞
(-1/11)⎜ -2 -5 3 ⎟
⎝ -4 12 -5 ⎠
Y-1=
⎛ 9 -16 3 ⎞
(1/44)⎜ -10 52 -18 ⎟
⎝ -3 20 -1 ⎠
If XA=Y then:
X-1XA=A=X-1Y=
⎛ 3 -9 1 ⎞⎛ 7 1 3 ⎞ ⎛ -1 0 1 ⎞
(-1/11)⎜ -2 -5 3 ⎟⎜ 1 0 3 ⎟=⎜ 2 1 0 ⎟
⎝ -4 12 -5 ⎠⎝ -1 -3 7⎠ ⎝ 1 -1 1 ⎠
This is the likely solution for A (shown in bold type).