Removing energy from neon gas may cause

Removing energy from neon gas may cause A huge decrease in motion and more attraction between particles..

The perimeter is just the sum of all the side lengths.
So let's get to work and addum up:

                              (2.3x + 14) + (2x) + (-0.2x + 15)

Add up all the x's:  (2.3x + 2x - 0.2x) =  4.1x

Add up all the ordinary numbers:  (14 + 15) = 29

So the perimeter is simply    4.1x + 29 .