SSC CPO 12 Mar 2019 Shift 2 Paper

The average of 18 numbers is 52. The average of the first 8 numbers Is 62 and the average of the next 7 numbers is 45. If the 16^th number is 6 less than the 17^th number and 17^th number is one more than the 18^th number, then what is the average of the 16^th and 18^th numbers?