The first meeting was 60 kilometers away from a place, that is to say, it is feasible for A to walk 60 kilometers. After two encounters, they walked three full distances, and A * * * walked 60 * 3 =180km.
The second time is 40 kilometers away from point A, 180+40 = 220 kilometers, which happens to be the whole journey from A to B and back to A, that is, 220/2 = 1 100 kilometers. Is the distance of AB.
1 10-60 = 50 is the answer to the question.