问题 解答题
(1)(9
2
7
+7
2
9
)÷(
5
7
+
5
9
)

(2)(1+
1
3
+
2
5
+
1
6
5
3

(3)
4
3
-
7
12
+
9
20
-
11
30
+
13
42
-
15
56

(4)
1
1×5
+
1
5×9
+
1
9×13
+
1
13×17
+
1
17×21
答案

(1)(9

2
7
+7
2
9
)÷(
5
7
+
5
9
),

=(9

18
63
+7
14
63
)÷(
45
63
+
35
63
),

=16

32
63
÷
80
63

=

1040
63
×
63
80

=13;

(2)(1+

1
3
+
2
5
+
1
6
)×
5
3

=

5
3
+
5
9
+
2
3
+
5
18

=

30
18
+
10
18
+
12
18
+
5
18

=

57
18

=3

1
6

(3)

4
3
-
7
12
+
9
20
-
11
30
+
13
42
-
15
56

=

80
60
-
35
60
+
27
60
-
22
60
+
13
42
-
15
56

=

5
6
+
13
42
-
15
56

=

35
42
+
13
42
-
15
56

=

8
7
-
15
56

=

64
56
-
15
56

=

7
8

(4)

1
1×5
+
1
5×9
+
1
9×13
+
1
13×17
+
1
17×21

=(1-

1
5
+
1
5
-
1
9
+
1
9
-
1
13
+
1
13
-
1
17
+
1
17
-
1
21
)÷4,

=(1-

1
21
)×
1
4

=

20
21
×
1
4

=

5
21

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