Can someone explain to me how to do this? (inverse of function)

Ricky takes out a $31,800 student loan to pay his expenses while he is in college. after graduation, he will begin making payments of $190.66 per month for the next 30 years to pay off the loan. how much more will ricky end up paying for the loan than the original value of $31,800? ricky will end up paying $ more than he borrowed to pay off the loan.

Indicate the formula for the following conditions: p^c(n,r)=

What is the sum of the first 8 terms of the geometric series