Find the inverse of this function (please show steps all of them)

Trish receives $450 on the first of each month. josh receives $450 on the last day of each month. both trish and josh will receive payments for next four years. at a discount rate of 9.5 percent, what is the difference in the present value of these two sets of payments?

How do i do this activity, is appreciated

The train station clock runs too fast and gains 5 minutes every 10 days. how many minutes and seconds will it have gained at the end of 9 days?