A=[1 -1  0] 
  [1  0 -1]  
  [6 -2 -3] 

B=[-2 -3 1]
  [-3 -3 1]
  [-2 -4 1]

     

Consider the minus sign before the 4 as a plus sign times (-4).
That's because we'd rather add matrices than subtract them:

     

Substitute the matrices in the equation for the letters:

 

Distribute the (-4) by multiplying it by all 9 elements of the 
matrix on the far right:

 

We add the corresponding elements of the matrices on the right:

 

Finally we multiply both sides by 




Distribute the  by multiplying it by all 9 elements of the 
matrix on the right:

   

Edwin