Title too long but please help

Question

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:

a) s for t = 3.5, the formula is: ? and for t=3.5 s = ?

b) t for s = 30, the formula is: ? and for s = 30 t = ?

Answer 1

s=60-12t

for t=3.5, s=60-12*3.5=18

for s=30, 30=60-12t, solve the equation, you get t=2.5