(1)2- (
5
6 +
3
10 ) ,
=2-
17
15 ,
=
13
15 ;
(2)
2
3 +
4
5 -(
3
5 -
1
15 ) ,
=
2
3 +
4
5 -
3
5 +
1
15 ,
= (
2
3 -
1
15 )+(
4
5 -
3
5 ) ,
=
3
5 +
1
5 ,
=
4
5 ;
(3)
5
6 -
7
9 +
3
4 ,
=
1
18 +
3
4 ,
=
29
36 ;
(4)
1
3 +
1
4 -
1
5 ,
=
7
12 -
1
5 ,
=
23
60 .