To get rid of the parentheses in the expression $a - b - (a - b)$, we need to distribute the negative sign across the terms inside the parentheses. Here's how it works:

$a - b - (a - b) = a - b - a + b$

Now, simplify the expression:

$a - a - b + b = 0$

So, the simplified result is $0$.

Do you want more details or have any questions?

Here are 5 related questions you could explore:

1. How do you simplify expressions with multiple sets of parentheses?
2. What happens when there are positive signs before parentheses?
3. How do you handle variables with coefficients inside parentheses?
4. What are the rules for combining like terms in algebra?
5. How would this expression change if there were exponents involved?

Tip: Always distribute signs carefully when removing parentheses, especially with subtraction to avoid errors!