What is the mistake NEED ANSWER ASAP

Answer:
The answers are in the image.
Step-by-step explanation:
Charlie made the mistake by not getting the equation equal to zero.
[tex]x^2 - 9x + 8 = 16[/tex]
Subtract 16 to both sides making it equal to 0.
[tex]x^2 - 9x - 8 = 0[/tex]
Using Quadratic Formula to Solve for x.