pls help me i'm sick... and i can't concentrate well and this is the final test to see if i will pass or not

If f(x)= 3x+6 which of the following is the inverse of f(x)

Acyclist bike x distance at 10 miles per hour .and returns over the same path at 8 miles per hour.what is the cyclist average rate for the round trip in miles per hour ?

If a company produces x units of an item at a cost of $35 apiece the function c=35x is a of the total production costs