Answer: 6 and 9, 7 and 8. 69, 78, 87, 96. So, there are only 4 combinations which would result in 15.
Step-by-step explanation:
Therefore the average sum of three numbers is 45:3=15. The number 15 is called the magic number of the 3x3 square. You can also achieve 15, if you add the middle number 5 three times. The odd numbers 1,3,7, and 9 occur twice in the reductions, the even numbers 2,4,6,8 three times and the number 5 once.
