Given these squares of numbers (maybe you can even solve it with just one!):
9 6 2
8 x 7
7 7 1
11 9 7 7 x 6 12 4 3
What is the value of x?
While the accepted answer is correct, the reasoning is actually a bit more involved:
All calculations are in the field $\mathbb{F}_{13}$ or $\mathbb{Z}/13\mathbb{Z}$.
The first two numbers in each row sum to the third.
The first two numbers in each column multiply to the third