Final answer:
The equation of the line of reflection is x = 8.
Step-by-step explanation:
To find the equation of the line of reflection, we need to determine the line that the point A (8, 7) is reflected across to become A' (8, 3).
Since the x-coordinate remains the same, we can conclude that the line of reflection is vertical.
Thus, the equation of the line of reflection is x = 8.
Learn more about Reflection across a line