Which one will replace the question mark?

For first triangle,

10 - 4 = 6

18 - 10 = 8

18 - 4 = 14

For second triangle,

14 - 8 = 6

22 - 14 = 8

22 - 8 = 14

For third triangle,

11 - 5 = 6

15 - 11 = 4

15 - 5 = 10.

915 - 364 = 551

and 789 - 543 = 246

Similarly, 863 - 241 = 622.

How the number is obtained?

2 + 4 = 6

5 + 9 = 14

Similarly,

3 + 5 = 8

Therefore, the answer is K₈.

Sum of numbers in lower half of the circle = 11 + 9 + 3 + 7 = 30

Sum of numbers in upper half of the circle = ? + 4 + 5 + 6 = ? + 15

Upper half = Lower half

30 = ? + 15

? = 30 - 15

? = 15.

Threfore, 15 is the answer.

3 x 5 x 4 = 60

and 5 x 7 x 4 = 140

Therefore, 4 x 4 x ? = 96

? = (96/16) = 6.

93 - (27 + 3) = 63

79 - (38 + 4) = 37

Therefore, 67 - (16 + X) = 42

X = 9

(0 + 2 + 6 + 4) - 2 = 10

and (6 + 2 + 10 + 8) - 2 = 24

Therefore, (4 + 14 + 12 + 10) - 2 = 38.

(4 + 9 + 2) = (3 + 5 + 7) = (8 + 1 + 6)

Total in each case = 15.

(5 + 3)/2 = 4

and (6 + 8)/2 = 7

Therefore (8 + 4)/2 = 6.

1 + 2 + 3 + 4 = 10

and 1 + 3 + 5 + 8 = 17

Similarly, 1 + 4 + 6 + 9 = 20.