Answer:
X and Y are complements
Explanation:
When two goods are complements, they experience joint demand. When the demand for one good increases, the demand for the other increases as well.
We know that as the price of a good falls, the demand for it increases. Therefore, we know that the demand for X increases because its price fell.
The problem also tells us that the demand for Y increased also. Since the demand for both X and Y increased when the price of good X fell, we know that these two goods are complements.
