How does the value of X change as Y decreases?

The relationship between X and Y depends on the specific context or equation in which they are related. If X is directly proportional to Y, then as Y decreases, X will also decrease. Conversely, if X is inversely proportional to Y, then a decrease in Y would lead to an increase in X. Without additional information about their relationship, we cannot determine the precise change in X as Y decreases.