The perimeter of any shape is the distance all the way around it.
For a triangle, it's the sum of the three side lengths.
I would normally copy them into my answer and then add them up.
But you've set them up in such a beautiful table in the question,
you can just look at that list and add them up.
Add up all the x's : x + x + x = 3x
Add up all the plain numbers: -3 + 2 + 4 = 3
There's your perimeter . . . . . 3x + 3 .