ON THE BLACKBOARD IS A 3×3 MAGIC SQUARE. THE SUM OF THE THREE NUMBE...

7. On the blackboard is a 3×3 magic square. The sum of the three numbers in each

row, each column and each diagonal is the same. As shown in the diagram

below, all but three of the numbers are erased. What is the number represented

by x in the cell at the upper left corner?

x

21 94

3

Answer :