as a sales gimmick, a cloth merchant began measuring the cloth with a yardstick that was x inches longer, beacuse of which his profit reduced from 50% of his cost to 20% of his cost. find x if 1 yard=36 inches.

Let CP of 1 yard be 180 Rs (just for the ease of calculation). So earlier he sold it for 270 . Now he is earning only 20% by selling it for 270 so CP = 270/1.2 = 225. So If the cost of 1 yard is 180, 225 will give 225/180 = 1.25 yard.
Thus required value is 9 inches.
Hope that helps.
Thanks