10-2[10-3(2+1)]
---------------
12/3(2)
10-2[10-3(2+1)]
= 10-2[10-3(3)]
= 10-2[10-9]
= 10-2[1]
= 10-2
= 8
For the denominator, I'm not sure what you mean
(12/3)(2) = 4*2 = 8
12/(3*2) = 12/6 = 2
In any case, just divide the top by the bottom.