ANSWER
6x + 8 or 2(3x + 4)
EXPLANATION
We are given that the three sides of the triangle are (x+ 4), 2(x - 1) and (3x + 6).
The perimeter of any shape is gotten by adding the lengths of all its sides together.
Therefore, the perimeter of the triangle is:
(x + 4) + 2(x - 1) + (3x + 6)
= x + 4 + 2x - 2 + 3x + 6
Collect like terms:
x + 2x + 3x + 4 - 2 + 6
= 6x + 8
= 2(3x + 4)
That is the expression for the perimeter of the triangle.
