Use the image to answer the question.

X. I Y
0. I 8
1. I 7.5
2. I 7
3. I 6.5

Which equation describes the function shown in the mapping diagram?

Based on the given mapping diagram, it can be observed that as x increases by 1, y decreases by 0.5. Therefore, the equation that describes this relationship is y = 8 - 0.5x.