Respuesta :
Nick's first step was to subtract 4x from both sides of the equation:
   3x - 4x + 9 = 4x - 4x - 5
       -x + 9 =  - 5
Charlie's first step was to subtract 3x from both sides:
   3x - 3x + 9 = 4x - 3x - 5
           9 = x - 5