Find the missing number.

Answer: Option B

First Method Row-wise Logic:
First element + second element = Third Element.
6 + 9 = 15
8 + 12 = 20
4 + 6 = 10
So, required number is 10.

Second Method
Logic:
Second Row element - first row element = Result * 2 = Third Row Element.
Column 1:
8 - 6 = 2
2 *2 = 4
Column 2:
12 - 9 = 3
3 *2 = 6
Column 3:
20 - 15 = 5
5 * 2 = 10.
Required Number is 10.

Third Method:
In the First row,
6*(3/2)= 9.
6*(5/2) = 15.
In the second row,
8*(3/2) = 12.
8*(5/2) = 20.
hence,
In the third row,
missing number,
= 4*(5/2) = 10.