What annual rate of interest will enable $800 to grow to $1000 in three years?

cant seem to derive the formula for this one, normal compound interest isnt working for me

2 answers

800 * (1 + i)^3 = 1000

this is with annual compounding
compound interest: 800(1 + r/100)^3 = 1000
simple interest: 800(1 + 3r/100) = 1000
solve for r and express as a %