To find that you first need to find what 9% is. You can multiply the number, 2,860 by .09 to find out your answer. That should be equal to 257.40. Since you now have that number, you can multiply it by 36. 257.40 is your average per month and you want to know by 3 years. So then your next step is 257.4*36 (there is 36 months in 3 years) which should be equal to 9,266.40.
