I don’t understand how to do this and i need help!!

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

The lengths of nails produced in a factory are normally distributed with a mean of 4.91 centimeters and a standard deviation of 0.05 centimeters. find the two lengths that separate the top 4% and the bottom 4%. these lengths could serve as limits used to identify which nails should be rejected. round your answer to the nearest hundredth, if necessary.

8. kelly wants to buy a magazine that is $25. later the magazine was marked up an additional 20%. what is the new price?