问题 解答题
7
15
+
4
15
+
8
15

3
7
+
1
5
-
8
35

3.52+
7
11
+
4
11
+6.48
2
3
-( 
8
9
-
5
6
)+
1
3
答案

(1)

7
15
+
4
15
+
8
15

=(

7
15
+
8
15
)+
4
15

=1+

4
15

=1

4
15

(2)

3
7
+
1
5
-
8
35

=

15
35
+
7
35
-
8
35

=

2
5

(3)3.52+

7
11
+
4
11
+6.48,

=(3.52+6.48)+(

7
11
+
4
11
),

=10+1,

=11;

(4)

2
3
-( 
8
9
-
5
6
)+
1
3

=

2
3
+
1
3
-( 
8
9
-
5
6
),

=1-

1
18

=

17
18

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