13×

2

3

+0.34×

2

7

+

1

3

×（-13）+

5

7

×0.34
=13×

2

3

+

1

3

×13+0.34×

2

7

+

5

7

×0.34
=13×（

2

3

+

1

3

）+0.34×（

2

7

+

5

7

）
=13×1+0.34×1
=13+0.34
=13.34．