To solve this expression, we need to follow the order of operations, which is parentheses, exponents, multiplication and division (from left to right), and addition and subtraction (from left to right).

First, let's simplify the expression inside the parentheses:

(-30 - 80 + 120) = 10

Now, we can substitute this value back into the original expression:

(70 + 20 - 60) - 10

Next, we perform the addition and subtraction from left to right:

70 + 20 = 90

90 - 60 = 30

Finally, we subtract 10:

30 - 10 = 20

Therefore, the final answer is 20.