The formula to calculate the final amount on an account that compounds interest is
A is the accrued amount
P is the principal amount
r is the interest rate expressed as a decimal value
t is the time period
n is the number of copounding periods, this saving's account compounds annualy which means that there is one compound period per year
For
P= $300
r=6/100=0.06
t=3 years
n (1/year) →3*1=3
The final amount after 3 years will be $358.53