2a-(3a+ab+b)

To simplify the expression \( 2a - (3a + ab + b) \), follow these steps:

1. Distribute the negative sign across the terms inside the parentheses: \[ 2a - 3a - ab - b \]

2. Combine like terms: \[ (2a - 3a) - ab - b = -a - ab - b \]

Thus, the simplified expression is: \[ -a - ab - b \]