Final answer:
The relationship between x and y is y - 1 = (4/5)(x - 2).
Step-by-step explanation:
To find the relationship between x and y if the points (2,1), (x,y), and (7,5) are collinear, we can use the idea that collinear points lie on the same line. The slope of the line passing through any two of the given points will be the same. We can use the formula for finding the slope between two points: slope = (change in y)/(change in x).
Using the given points (2,1) and (7,5), we can find the slope as: slope = (5-1)/(7-2) = 4/5.
Therefore, the relationship between x and y is: y - 1 = (4/5)(x - 2).