To find the total amount of interest for the 6 years, we can do $3967.50 minus $3450 which is 517.5.
Next divide 517.5 by 6 to find the interest every year which is 86.25.
This means that x% of $3450 is 86.25. This can be written as x/100 x $3450 = 86.25 To find x, we divide 86.25 by 3450 to get 0.025 Finally multiply by 100 to get an interest rate of 2.5%.