#### Answer

$f(g(x))=-\dfrac{8}{5}x-23$
$g(f(x))= -\dfrac{8}{5}x+\dfrac{29}{5}$

#### Work Step by Step

Substitute g(x) in f(x):
$f(g(x))= -8(\dfrac{x}{5}+4)+9=-\dfrac{8}{5}x-23$
Substitute f(x) in g(x):
$g(f(x))= \dfrac{-8x+9}{5}+4 = -\dfrac{8}{5}x+\dfrac{29}{5}$