Given a board of $3 \times 3$
Source: May Olympiad 2016 L1 P4
March 14, 2021
combinatorics
Problem Statement
Given a board of you want to write the numbers and a number in their boxes positive integer , not necessarily different from the above. The goal is that the sum of the three numbers in each row be the same
Find all the values of for which this is possible.
For which of the values of found in is it possible to arrange the numbers so that no only the three rows add the same but also the three columns add the same?