Answer:
If x = 20, then y = 12.5/20 = 0.625
Explanation:
The pertinent relationship is y = k/x, where k is the constant of proportionality.
Subbing 5 for y and 2.5 for x yields 5 = k/2.5, so k = 12.5.
Then the specific relationship fit to this problem is y = 12.5/x.
If x = 20, then y = 12.5/20 = 0.625