simplify the expression

To simplify the expression \((9m - 3) - (2m + 12)\), follow these steps:

1. Distribute the negative sign across the second parentheses:
\[
9m - 3 - 2m - 12
\]

2. Combine like terms:
- Combine the \(m\) terms: \(9m - 2m = 7m\)
- Combine the constant terms: \(-3 - 12 = -15\)

Putting it all together, we get:
\[
7m - 15
\]

So, the simplified expression is:
\[
\boxed{7m - 15}
\]