39÷

13

10

=30（0.21+0.7）÷7=0.13（

1

4

-

1

5

）×20=1（0.56+0.69）×8=10

1

3

×3÷

1

3

×3=911.75-（1

3

4

+5）=5 7-4÷

4

7

=02-

2

5

×

2

5

=1

21

25

．