First of all, this is a big "being prime minister" on behalf of me. It was solved yesterday, but I don't know why it didn't show up when I saw it this morning. So, I created a new number today. Please call again with sadness. To do this kind of problem, first look at the picture carefully, and then find faults in the picture. Maybe you are a little confused when you look at it. That's because you don't know enough about this process, so I'll help you find fault on the way first. Set several points before doing the problem. There are four points in the function image. The first point has been given to O, and the other three points are set to Z, H, Y, H and Y from left to right respectively. Look at the diagram I gave you first. I have set all the points so that it is convenient for us to analyze the problem. First of all, we should know that this picture shows the distance between Party A and Party B by time. Of course, if we divide the time, we can get the value of relative speed. The distance between two people is getting farther and farther, because A is faster, but why is the distance between two people getting smaller at Z? Because A has reached the finish line, it takes 3 hours for A to reach the finish line. Then let's look at the second half, why not a straight line but a broken line? What does the breakpoint need to change? Since it is a broken line, the relative speed of the two people will change, and the moment of change is at the folding point H, so let's look at the topic again. It turns out that when A comes back, the speed is not always the same. He didn't move for the first hour, and then he went to see B for the rest of the time. Then in the first hour, the relative speed of the two people is relatively small, and it is slow in a straight line, but when the two people start to move relatively, it is steep in the image. To sum up, if two people walk in the opposite direction in ZH A section and HY section, the abscissa of point H will come out, which is one hour larger than the abscissa of z 3+ 1=4. What about the ordinate? So we began to understand the first question (1). The distance between the two people has been shrinking in this hour, shrinking by S kilometers. This S kilometer has not been moved through the analysis of question A, so it is all taken by B. The speed is multiplied by time 1*60=60 kilometers, which means that the distance between two people is reduced by 60 kilometers between 3 hours and 4 hours. That is, the ordinate of Z is 60 larger than that of H, so the ordinate of H is 120-60 = 60 (2). Find the function image between one car returning (H point) and two cars meeting (Y point). Then we all know the coordinates of these two points, H (4 4,60) and Y (4.4,0), and just substitute them into Y = KX+B, hehe (3) Find the time for A to return. The corresponding time for a return is 4 hours to 4.4 hours. In this 0.4 hour, we know the four values of time, distance and speed distance of B = time * speed (A+B). When the known quantity is one generation, the speed a comes out. See two places where Big Brother V=90 (km/h) upstairs for the results. We are analyzing B. We have been running for 4.4 hours from beginning to end, and we haven't reached the finish line yet. He escaped from Pluralism? =60*4.4=264 kilometers, but there is still a section left, which A helped him run before he came back to meet B. How much did he run? =90*0.4=36 km, then the distance comes out =264+36=300 km. Well, here's the problem. I hope my nonsense will not only help you do this problem, but also help you learn how to do it. It is very important to try to find out what you think is abnormal. This is the breakthrough. Hehe, don't want to say too much. I hope your math can be greatly improved. This is my qq number 78 10 16898. If you have any questions (only math, of course), you can ask me. Although I haven't been doing it for a long time, I will try my best to help you if it can be solved. I think this will also supplement my mathematical thinking.

Please accept it, thank you!