4 is the missing digit. 37= (2+1 2+5) 3 7

So 92= (3+5 8+4) 8 12 8+1 2 9 2

This question is ambiguous. Besides 4, -5 is also possible by following logic, :

3+7 = 5+1+2+2 9+2 = 8+3+5+(-5)

Atleast one more graph should have been provided or it should be mentioned that answer is confined to natural numbers.

Which number replaces the question mark - 12, 9, 7, 3, 4, 6, ??