He’s paying $258 every 3 months, there’s 12 months in a year. This will then give you 12 divided by 3 which is for the number of payments for 1 year, this gives you 4. You then take the $258 multiply by 4 to get 1,032. Take that number the 1,032 multiply by 3 for the number of years to get 3,096 for total payments for the course of 3 years.
Hope this helps!