The longest side of a triangle is 3 times the shortest side and the third side is 2 cm shorter than the longest side. If the perimeter of the triangle is at least 61cm, find the minimum length of the shortest side.

Let the shortest side of the triangle be of length x cm
  The length of the longest side = 3x cm
      The length of the third side = (3x - 2) cm
      It is given that the perimeter is at least 61 cm
  Perimeter 
Hence, the minimum length of the shortest side = 9 cm.