Answer:
Base of the original triangle is 12 cm.
Step-by-step explanation:
Let base of triangle be x Â
two equal legs  of triangles by y
therefore perimeter of triangle
            x+y+y = 50 or x+2y =50
according to the question
 if base is x+3 and leg is y-4
then both are equal
  that is x+3 = y-4
      y-x = 7 or y =x+7
  x+2y =50
  x+2(x+7) = 50
  x+2x +14 =50
   3x +14 =50
   3x = 50 -14
   3x = 36
   x = 12
therefore base of the original  triangle is 12 cm          Â