Answer:
A - B = [ -1 3 ]
 [ -6 2 ]
 [ -4 -10 ]
Explanation:
Since Matrix A and Matrix B have the same size, then we can simply perform the operation of subtraction on each position within the matrices to get the resulting subtracted matrix. 
A = [ 4 7 ] B = [ 5 4 ]
 [ -3 8 ] [ 3 6 ]
 [ -5 -2 ] [ -1 8 ]
A - B = [ (4 - 5) (7 - 4) ]
 [ (-3 - 3) (8 - 6) ]
 [ (-5 - -1) (-2 - 8) ]
A - B = [ -1 3 ]
 [ -6 2 ]
 [ -4 -10 ]
Cheers.