Well since we don't know the measurements of said triangle, I can only give you the formula for perimeter of a triangle.
Add each side length together to get the perimeter. For example, say we have a triangle with the side lengths 8, 9, and 3. To find the perimeter of this triangle, add each side length together.
8 + 9 + 3 = 20
The perimeter would be 20, or the sum of the given sides.