Me i need to do this before i go to sleep and i am sooo tired and do not understand how to do this. (don't /answer if you don't know.) i need to know if i put 5,309 dollars into a saving account for 4 years. how much interest does it need to be for the 5,309 dollars to be 21,236 after for years.

Ok so, here goes:
simple interest: r- rate, A- amount in the end, t- time, P- principal
r = (1/t)(A/P - 1)
Putting in our numbers
r = (1/4)((21236/5309) - 1) = 0.75
r = 0.75

Converting r decimal to R a percentage
R = 0.75 * 100 = 75%/year

The interest rate required to get a total amount, principal plus interest, of $21,236.00 from simple interest on a principal of $5,309.00 over 4 years is 75% per year.