If s the number of seconds, which variable expression represents the phrase below?

Acable car begins its trip by moving up a hill. as it moves up, it gains elevation at a constant rate of 50 feet/minute until it reaches the peak at 2,000 feet. then, as the car moves down to the hill’s base, its elevation drops at the same rate.

For how answer my question this will be the last question can you answer in math subject

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?