Inferior Goods- Unfortunately someone got an unexpected pay cut and is now making half the money they did before. They would get a used car due to their money running low.
Due to their reduced income their demand for a used car will go up.
Nike came out with new basketball shoes and everyone is loving them.
Since the demand on Nike went up the demand on Adidas went down.
Adidas and Nike are both shoe companies, with the success of one company we can assume that the sales of the other went down; they have an inverse relationship.