=320×5/32×22/5

= 220km

2,66+66× 2/33 = 7 billion;

3. Original price = 320 ÷ (1-68%) =1000 yuan;

4, can't see clearly;

5、4/5× 1/7÷2/5

=4/5× 1/7×5/2

=2/7;

1/9×9÷( 1/9×2 1)

= 1/9×9÷ 1/9÷2 1

= 1/9×9÷ 1/9÷2 1

= 1×9× 1/2 1

=3/7;

4.5x+x= 12/ 17

Solution:11/2x =12/17.

x = 12/ 17×2/ 1 1

x = 24/ 187；

x÷7/8= 1/4+0.25

Solutions; x×8/7= 1/4+ 1/4

x= 1/2×7/8

x=7/ 16