3:7:8 what the ratio?

Using compound interest, it is found that Melanie would need to invest a value of $7,710.

What is compound interest?

The amount of money earned, in compound interest, after t years, is given by:

A(t) is the amount of money after t years.  P is the principal(the initial sum of money).  r is the interest rate(as a decimal value).  n is the number of times that interest is compounded per year.  t is the time in years for which the money is invested or borrowed.

In this problem, we have that:

Rate of 3.1%, hence .Compounded daily, hence .Value of $11,900 in 14 years, hence .The amount she needs to invest is P.

Hence:

Melanie would need to invest a value of $7,710.

To learn more about compound interest, you can take a look at link