1. According to "Xiao Wang can run twice and Uncle can run three times", the speed ratio of two people is 2: 3, so let Xiao Wang's speed be x and Uncle's speed be 1.5x, and get the equation:

(x+ 1.5x)*32=400

2.5x*32=400

80x=400

x=5

So Xiao Wang's speed is 5 meters per second, and Uncle's speed is 5* 1.5=7.5 meters per second.

When running in the same place and direction, the time required for two people to meet is:

400÷(7.5-5)

=400÷2.5

=160second

2. If the expressway is x kilometers long, it is x+30 kilometers before the expressway is opened, and the equation is obtained:

x÷4-30=(x+30)÷7

7x-840=4x+ 120

3x=960

x=320

So the expressway between the two places is 320 kilometers long.

3. Let A catch up with B in x hours and get the equation:

3x=2*3+2x

x=6

So it took A 6 hours to catch up with B, and the dog ran 3+6=9 hours, so the dog ran 9×5=45 kilometers.