Taking x as any number:
Eight times a number means 8x.
The sum of the number and nine is x+9
Now, eight times a number added to the sum of the number and nine is 8x+(x+9).
It means that the expression is:
[tex]8x+(x+9)[/tex]If you want to reduce similar terms you can also write:
[tex]9x+9[/tex]