Jenny wants to give her 14-year-old daughter $20,000 when she turns 18. How much does she need to put in the bank now if the interest rate is 10 percent per year?

let's suppose it's her birthday (in a few days)

Considering the interest rate by the end of the period she would have to had gathered 18 000 in the account which represents whatever g sum she has put together in the first 3 years + 10%of that sum+what she has to add in the forth year and so on so she can deposit the sum she's got so far