Question

http://prntscr.com/lsvrj0

Answer 1

The formula for compound interest is
\(A = P\left(1 + \dfrac{r}{n}\right)^{nt}\)

Where A = the computed amount (In this case 8500)
P = the Principal
r = interest rate (in this case 5%)
n = number of times compounded (in this case 12)
t = length of time the account is open (in this case 21 years)

Answer 2

BTW, you can quickly isolate \(P\) by dividing both sides by \(\left(1 + \dfrac{r}{n}\right)^{nt}\)

Answer 3

Let me know what you get for \(P\) @shirt