How would i solve this... Louis opened a savings account 15 years with a deposit of $2,705.76. The account has an interest rate of 3.9% compounded twice a year. How much interest has Louis earned? what would the formula look like? and what is the number for "twice a year"?

Well if it's like half years, then 15 years = 30 half years.

Do you know the formula for continuous compounding?

no

It's something like if you're compounding 5% of 100 every year, then you'll have: \(\Large \color{MidnightBlue}{\Rightarrow 100(1 + 5\%)^{years} }\)

so P(1+R/2)^2*15?

If you want to see the interest, then you will have to subtract the principal from the amount.

And no.

\(\Large \color{MidnightBlue}{\Rightarrow 2,705.76(1 + 3.9\%)^{30} }\)

Remember that I put 30 because of half years

OK I GOT IT THANKS