A bicyclist traveled with a speed of 12 km/h from a camping ground to a station, located 60 km away. Write a formula expressing the dependence of the variable s on t, where s is the distance between the bicyclist and the station in km, t - the duration (time) of his travel in hours. Using the formula, find s for t=3.5 AND t for s=30 (AND = separate)

The bicyclist starts at the camp and travels 12 km/h. So in t hours, the bicyclist travels 12t km.  The remaining distance (from the bicyclist to the station) is 60 - 12t, the whole distance, 60 km minus the distance the bicyclist has traveled.

[tex]s=60-12t [/tex]

Now you can answer questions such as "how far was the bicyclist from the station after 3 hours?"  Substitute 3 for t.  s = 60 - 12(3) = 60 - 36 = 24 km.