The rule of the compounded interest is
A is the final amount
P is the amount each year
r is the interest rate in decimal
t is the time
n is the number of periods per year
Since you deposit $3000 each year, then
P = 3000
Since the annual rate is 8%, then
r = 8/100 = 0.08
n = 1
Since the time is 20 years, then
t = 20
Substitute them in the rule above to find A
You will earn $137 285.8929 after 20 years