问题 解答题
4
5
-(
7
10
-
13
20
9
10
-(
1
6
+
2
3
11
12
+
5
8
+
3
8
+
1
12
5-
3
7
-
4
7
答案

(1)

4
5
-(
7
10
-
13
20
),

=

4
5
-
1
20

=

3
4

(2)

9
10
-(
1
6
+
2
3
),

=

9
10
-
5
6

=

1
15

(3)

11
12
+
5
8
+
3
8
+
1
12

=(

11
12
+
1
12
)+(
5
8
+
3
8
),

=1+1,

=2.

单项选择题
单项选择题