Here, f = {(3,a),(4,b),(7,c)}. i.e., f(3) = a, f(4) = b and f(7) = c

Also, g = {(x,3),(y,4),(z,7)}. i.e., g(x) = 3, g(y) = 4 and g(z) = 7

Now,

f_{o}g = f(g(x))

So, f(g(x)) = f(3) = a

f(g(y)) = f(4) = b

f(g(z)) = f(7) = c

Hence the ordered pair representing f_{o}g = {(x,a),(y,b),(z,c)}

The function diagram