Then A crawled for (x+2) minutes.

The distance between them is the same.

So 40(x+2)=50x= total series.

Suppose it takes x hours to get from a to b.

Coming and going is the distance between a and B.

Therefore,100x = 80 (5-0.5-x) = the road between A and B.

Set the express train to leave x hours before the two cars meet.

The total distance between two cars is two stops.

Therefore, 60(x+32/60)+ 100x=448.

4. Suppose that A and B are 1 apart.

Then the first speed is 1/2 and the second speed is 1/3.

Assemble a and b in x hours.

The total distance between Party A and Party B is the distance between AB.

So1/2x+1/3 (x+1) =1.

5. 1 person, it takes 20 hours. Let's assume that the total workload is 1, so everyone works 1/20 per hour.

Suppose there are x people involved in sorting out the data at first.

The sum of the workload of two people is 1.

So 2 * (1/20) x+4 * (1/20) (x+2)

6. Let the side length of each small square iron sheet cut be x cm.

The original square iron sheet has a side length of 50+2x.

The volume is 45,000 cubic centimeters, and the side length of each small square iron piece is the height of a rectangular box without a cover.

So 50*50x=45000.

7. Suppose Xiaoming walked for x hours.

Then it took (1-x) hours by car.

Walking distance+bus distance = distance from home in the park (provided that you don't go back and detour)

So 5x+30( 1-x)=25.