(1)456-199,
=456-200+1,
=256+1,
=257;
(2)0.25×5.7×4,
=0.25×4×5.7,
=1×5.7,
=5.7;
(3)252÷24-0.4×6,
=10.5-2.4,
=8.1;
(4)(3.8-1.8÷2)×
,1 2
=(3.8-0.9)×
,1 2
=2.9×
,1 2
=1.45;
(5)(8+
)÷4,4 9
=(8+
)×4 9
,1 4
=8×
+1 4
×4 9
,1 4
=2+
,1 9
=2
;1 9
(6)4.4-
+1.6-1 5
,4 5
=(4.4+1.6)-(
+1 5
),4 5
=6-1,
=5.