(3x-9)-(x-4)=15

To solve the equation \((3x - 9) - (x - 4) = 15\), follow these steps:

1. Distribute the negative sign across the second parentheses: \[ 3x - 9 - x + 4 = 15 \]

2. Combine like terms: \[ (3x - x) + (-9 + 4) = 15 \] This simplifies to: \[ 2x - 5 = 15 \]

3. Add 5 to both sides of the equation: \[ 2x - 5 + 5 = 15 + 5 \] Simplifying gives: \[ 2x = 20 \]

4. Divide both sides by 2: \[ x = \frac{20}{2} = 10 \]

Therefore, the solution is: \[ x = 10 \]