The perimeter of the triangular park shown on the right is 16x-6. what is the missing length? 2x+2 and 5x-4 find the missing length

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

The answers are 20,30,80,180,960,890,1230,4560. on the first row