Therefore, A has walked 7/ 16 of the whole journey, and there is still (1/2-7/16 =116) from the midpoint of the whole journey.

Therefore, 30 kilometers is116, and the whole journey is 30 * 16 = 480 kilometers.

2. if b has x yuan, a has 5X yuan.

5X-40=7*(X-40)

So x = 120.

So, A has 600 yuan and B has 120 yuan.

There are x people.

(5X/ 12)+(7X/ 15)+(X/5)= 65

The solution is x = 60.

So there are 60 people.

4.a works 8 days. That B worked for 4 days, A finished it every day 1/8, and B finished it every day 1/4.

Two people together, one day (1/8)+( 1/4) = 3/8.

So it takes 1/(3/8) = 8/3 days to complete the cooperation.