Perimeter is the sum of all sides of a polygon. For this case, the perimeter is expressed as: P=a+b+c. It has been said that the longest side is twice that of the shortest side. Let's assume that a is the longest side and b is the shortest side. So, the equation for the shortest side is,
6.2 = 2c
c = 3.1
14.5 = 6.2 + 3.1 + b
14.5 = 9.3 +b