①原式=-15+6=-9；    

②原式=6×26×

1

3

×

6

13

=24；   

③原式=-（

11

12

×48-

7

6

×48+

3

4

×48-

13

24

×48）=-（44-56+36-26）=2；    

④原式=-25-[-8-（1-

4

5

×

3

4

）×

1

2

]=-25-[-8-

2

5

×

1

2

]=-25+8+

1

5

=-16

4

5

．