问题 解答题
计算下面各题.
7
8
-
2
13
+
1
8
2
3
+
1
6
-
1
9
1-
1
5
-
1
5
7
9
-(
1
5
-
1
10
答案

(1)

7
8
-
2
13
+
1
8

=

7
8
+
1
8
-
2
13

=1-

2
13

=

11
13

(2)

2
3
+
1
6
-
1
9

=

12
18
+
3
18
-
2
18

=

13
18

(3)1-

1
5
-
1
5

=1-(

1
5
+
1
5
),

=1-

2
5

=

3
5

(4)

7
9
-(
1
5
-
1
10
),

=

7
9
-(
2
10
-
1
10
),

=

7
9
-
1
10

=

61
90

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