Find the missing number?

Answer: Option C

Left to Right
First Circle :
1 + 3 +2 + 1 + 0 + 5 = 12
Second Circle:
2 + 7 +0 + 1 + 4 + 1 = 15
Third Circle:
2 + 1 + 4 = 0 +7 + 4 = 18
Similarly, sum will follow the sequence,
12, 15, 18, 21, 24, 27.
So, In last Circle,
5 + 8 + 3 + x + 6 + 4 = 27
26 + x = 27
x = 1