Solution: It takes 4+3=7 hours for a car to travel all the way.
In other words, when they met, A walked 4/7 of the whole journey.
Then B walked 3/7 of the way.
Speed ratio of Party A and Party B = distance ratio = 4/7: 3/7 = 4: 3 = 1: 3/4.
So the speed of a car = 20/(1-3/4) = 80 km/h.
AB Distance =80×7=560 km
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