Answer:
(fog)(x) = x
Explanation:
Composite function:

Composite of a function and its inverse.
The composition of a function and it's inverse is the straight line x. So

f = {(1,6), (4,7), (5,0)) and g = {(6,1), (7,4), (0,5)}
We can see that the x-values in f are the y-values for g, and the y-values for f are the x-values for g, that is, f and g are inverse functions. Thus:
(fog)(x) = x