(1)解:$(-0.25)×3×(+4)$
$=(-0.25)×(+4)×3$
$=-1×3$
$=-3$
(2)解:$(-\frac{5}{6})×(-2.4)×(+\frac{4}{5})$
$=(-\frac{5}{6})×(-\frac{12}{5})×(+\frac{4}{5})$
$=2×\frac{4}{5}$
$=\frac{8}{5}$
(3)解:$8×(-\frac{3}{4})×(-4)×(-2)$
$=8×[(-\frac{3}{4})×(-4)]×(-2)$
$=8×3×(-2)$
$=24×(-2)$
$=-48$
(4)解:$8×(-\frac{3}{4})×0×(-4)×(-2)=0$
(5)解:$4×(-12)+(-5)×(-8)+16$
$=-48 + 40 + 16$
$=(-48 + 40) + 16$
$=-8 + 16$
$=8$