In 1 year, you add 5.5% of what you had a year ago (P).
So after the first year, you have:
Maturity, M1 = P + (5.5/100)*P = P(1+0.055)
After the 2nd year,
M2 = M1 + (5.5/100)*M1 = M1(1+0.055) = P(1+0.055)(1+0.055)
After 3rd year,
M3 = M2 + (5.5/100)*M2 = M2(1+0.055) = P(1+0.055)(1+0.055)(1+0.055)
There is a noticeable trend for compound interests:
Compound Amount, A = P(1+r)t
where r is the rate per year, and t is the number of years.
Straightforward answer:
Compound Amount, A = 6200(1+0.055)3
A = $7280.30
Compound Interest = A - P
= $7280.30 - $6200.00
= $1080.30