The perimeter of a Triangle is the sum of three sides ; ie assuming k,l,m be the three sides of a triangle means then k+l+m = perimeter of a triangle.
here given that a two sides lengths are 2x+ 2 and 5x-4 ;
and the perimeter length is 16x-6;
let the unknown side be k;
therefore k + 2x+2 + 5x-4 = 16x-6;
resolving k + 7x-2 = 16x-6;
Ans:- k= 16x-6-7x+2 = 9x-4 ie the unknown length k is 9x-4