When simplified, 9x – (x + 1) is: 8x – 9x. 8x + 1. 8x – 1. None of the choices are correct.

Using basic subtraction I believe the answer would be 8x-1

If you want to solve it, you can turn 9x - (x + 1) into 9x - x - 1, which turns into 8x - 1