G borrowed $15,000 to buy a business. The interest rate was 11%. If G paid all the interest and the amount borrowed with a single payment at the end of 16 months, what is the amount of this payment ? please help solve with details

Afitness center has 2 membership plans one has a low dollar sign up fee of 15 dollars and costs 38 dollars per month to join. a second plan has a higher sign up fee of 78 dollars but a lower monthly fee of 31 dollars for what number of days of the month is the coat the same