(1)24.56-
-4.56-4.75,1 4
=24.56-0.25-4.56-4.75,
=(24.56-4.56)-(0.25+4.75),
=20-5,
=15;
(2)4.2×5.43+4.57×4.2,
=4.2×(5.43+4.57),
=4.2×10,
=42;
(3)6035-450÷30×15,
=6035-225,
=6000+35-(200+25),
=(6000-200)+(35-25),
=5800+10,
=5810;
(4)
÷[2 3
÷(5 9
-7 8
)],1 4
=
÷[2 3
÷5 9
],5 8
=
÷[2 3
×5 9
],8 5
=
÷2 3
,8 9
=
×2 3
,9 8
=
.3 4