V= speed. S= distance, t= time.
vt=s,s/t=v,s/v=t。
Note: Distance is not necessarily the distance to meet. The distance traveled should be calculated from the moment when two cars (or people) "leave" at the same time.
For example, A walked from A to B for 1 hour, and then B walked from B to A. T hours later, the two met, with a distance of S kilometers.
S kilometers here is the distance to meet, but not the distance from A to B. An hour's walking distance between S and A is the distance from A to B. 。