Wang Hua listened for 90 minutes. Subtract 90 minutes from 15: 20 to get 13: 50.

2

A calls 1/6 every hour.

I dial110 every hour.

B gives 7/ 10, and A gives 3/ 10.

A It took 3/10/(1/6) =1.8 hours.

three

It is 7x long and 4x wide.

7x-4x= 12

x=4

Chang 28

Width 16

four

The ratio of arrival speed to departure speed is 7: 6.

The time ratio is 6: 7.

It took 52*6/ 13=24 minutes to arrive.

Distance 24*70= 1680m.