Aprincipal of $3800 is invested at 6.75% interest, compounded annually. how much will the investment be worth after 6 years?

Your principal amount is = 3800$.
your interest for the compound interest is equal to 0.0675/6
and your compounding period is equal to 6.
so now Fv=a(1+rt)^n
therefore
Fv=3800(1+(0.0675/6))^6
what ever this works out to be will be your answer.
Fv variable just means "future value."
The rest is self explanatory.