Question

a triangle whose perimeter is 3 times the length of its side

Answer 1

Equilateral triangle

Answer 2

let,perimeter of triangle be x
    side of a triangle be 'a' 
Given,
   x=3a
⇒x=a+a+a
This is only possible when the triangle is equilateral.
∴ In, equilateral triangle perimeter is 3 times the length of side of a triangle.