The mileage of the railway from a to B is 480 km. From a to B, the train a with the word "g" and the train B with the word "d" can go directly to B. It is known that the average speed of train a is 40 km / h faster than that of train B, and the running time is 2 hours less than that of train B_____________ I can't ask the average speed and driving time of car a because I use my mobile phone to ask questions, Three hours or four hours

The mileage of the railway from a to B is 480 km. From a to B, the train a with the word "g" and the train B with the word "d" can go directly to B. It is known that the average speed of train a is 40 km / h faster than that of train B, and the running time is 2 hours less than that of train B_____________ I can't ask the average speed and driving time of car a because I use my mobile phone to ask questions, Three hours or four hours

So 480 / x + 2 = 480 / (x-40) 480x-40 * 480 + 2x squared - 80x = 480xx squared - 40x-9600 = 0x squared - 40x + 400 = 10000 (x-20) squared = 10000x-20 = plus minus 100x1 = 120x