Me simplify 3x-2x+x-9. i was told my answer was wrong

The answer is:  " 2x − 9 " .

Explanation:

Given:  3x − 2x + x − 9 ; Simplify the expression ;

  3x − 2x + x − 9 ;

= 3x − 2x + 1x − 9 ;

Note that:  "3x − 2x + 1x" are "like terms" that appear in sequential order; 

So:  "3x − 2x = 1x ; 

and:  1x + 1x = 2x ; 

And then write down the " − 9 " ;

     " 2x − 9 " .

The answer is:  " 2x − 9 " .