-(11a+b)-(12a-3b)

To simplify the expression \(- (11a + b) - (12a - 3b)\), let's first distribute the negative signs:

1. Distribute the negative sign on the first term: \[ - (11a + b) = -11a - b \]

2. Distribute the negative sign on the second term: \[ - (12a - 3b) = -12a + 3b \]

Now, we can combine the two results:

\[ -11a - b - 12a + 3b \]

Next, combine like terms:

• Combine the \(a\) terms: \[ -11a - 12a = -23a \]

• Combine the \(b\) terms: \[ -b + 3b = 2b \]

Putting it all together, the simplified expression is:

\[ -23a + 2b \]