①

5

12

×

1

13

-

1

4

÷13   
=

5

12

×

1

13

-

1

4

×

1

13

=（

5

12

-

1

4

）×

1

13

=

1

6

×

1

13

   
=

1

78

                
②3.5×98+35×0.2
=35×9.8+35×0.2
=35×（9.8+0.2）
=35×10
=350