$800 at 4.25% intrest for 6 years

To solve this (assuming that you mean simple interest) you need to first know the formula for exponential growth witch is S(1+(-)I) so with all of are numbers inputed it looks something like this 800(1+.0425) because,
S=starting amount, I=interest rate, and T=Time (amount of time that goes by) 
back to the equation it would equal 1027 (rounded to the nearest dollar)

Enjoy!=)