>>> A=[[2,-1,3],[4,-2,0],[-3,3,6]]
>>> B=[[ 1,3,11],[7,9,17],[13,15,5]]
>>> 3*A-2*B
Traceback (most recent call last):
  File "<pyshell#37>", line 1, in <module>
    3*A-2*B
TypeError: unsupported operand type(s) for -: 'list' and 'list'