1, solution: Let the train speed be x m/s and the train length be y m. 。
From the topic: 45x=800+y
35x=800-y
Solution: x=20
y= 100
A: The train speed is 20 meters per second and the length is 100 meters.
2, speed and x2 = 20km; Speed difference ×2=2 km.
Solution: let the speed of a be xkm/h and the speed of b be ykm/h,
Judging from the title: 2(x+y)=20
2(x-y)=2
Solution: x=5.5
y=4.5
A: A's speed is 5.5 km/h and B's speed is 4.5 km/h. 。