Start with the innermost brackets (10-8)=2; now move the next brackets: 4-2x2+12/6x1, where we substituted the result 2 from the first brackets into its place in the second lot of brackets. So now we do the multiplication and division because they have higher priority than addition and subtraction. So we get 4-4+2 which comes to 2.
We are now left with 3x2-6 as the final result and this comes to zero because we multiply 3 by 2 before subtracting 6, and 6-6=0.