Final answer:
When the price of good X decreases and demand for good Y increases, goods X and Y are likely complements, as their consumption is interdependent.
Step-by-step explanation:
If the price of good X decreases and the demand for good Y increases, then goods X and Y are likely complements. This scenario indicates a negative cross-price elasticity of demand, meaning that the goods are used together, and the consumption of one enhances the consumption of the other. In the case of complements, a lower price for good X leads to an increase in demand for good Y since buyers tend to use these goods together. Examples of complementary goods include gasoline and automobiles, or pasta and pasta sauce.