To find the perimeter of the triangle you need to add up all the side lengths
[tex]2x - 7 + 5x - 3 + 2x - 2[/tex]
Now move like terms, the ones with x and ones without, next to each other.
(You can skip this step, but I think it makes it easier to understand.)
[tex]2x + 5x + 2x - 7 - 3 - 2[/tex]
Now just add like terms to get your answer.
[tex]9x - 12[/tex]
