脱式计算.[90-(18.9+2.88)]÷1.8 4×(2.44-1.8)÷0.4 4 5 - 2 3 +( 3

脱式计算.[90-(18.9+2.88)]÷1.8 4×(2.44-1.8)÷0.4 4 5 - 2 3 +( 3 5 - 1 15 )      4 5 -( 3 20 + 3 10 )+ 3 4 .

(1)[90-(18.9+2.88)]÷1.8,
=[90-21.78]÷1.8,
=68.22÷1.8,
=37.9;

(2)4×(2.44-1.8)÷0.4,
=4×0.64÷0.4,
=6.4;

(3)
4
5
-
2
3
+(
3
5
-
1
15
),
=
4
5
-
2
3
+
3
5
-
1
15

=(
4
5
+
3
5
)-(
2
3
+
1
15
),
=
7
5
-
11
15

=
2
3


(4)
4
5
-(
3
20
+
3
10
)+
3
4

=
4
5
-
9
20
+
3
4

=
16
20
-
9
20
+
15
20

=
11
10
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