Fof x equals four divided by x.
and g of x equals four divided by x

F(x)=8/x, g(x)=8/x
f(g(x)) = f(8/x)=8/8/x=x,
g(f(x)) =g(8/x) =8/8/x=x,
so f(g(x)) = g(f(x)) = x. if f of x equals eight divided by x and g of x equals eight divided by x