Find the missing number from the given alternatives.

6	10	14
9	15	21
12	20	?

The correct option is 28.

Let us analyze the relationships between the numbers in the columns and rows of the given grid:

Row 1 consists of the numbers: 6, 10, and 14.
Row 2 consists of the numbers: 9, 15, and 21.
Row 3 consists of the numbers: 12, 20, and the missing number represented by '?'.

If we look closely at each row, we can express the relationship between the first, second, and third numbers in the row. Let the numbers in a row be $A$, $B$, and $C$ respectively.

For Row 1:
The first number is 6, and the second is 10. The sum of these two is:
$6+10=16$
This is not equal to the third number (14), but we can see another relationship. If we divide the first number by 3 and multiply it by 7, or if we look at the ratios of the numbers: 6, 10, 14 are in the ratio:
$6:10:14=3:5:7$

Let us check if this ratio holds for Row 2:
The numbers are 9, 15, and 21. If we divide each by 3, we get:
$\frac{9}{3}=3$
$\frac{15}{3}=5$
$\frac{21}{3}=7$
So, the numbers in Row 2 are also in the ratio $3:5:7$.

Alternatively, the pattern for each row can be written as:
$C=\frac{A\times 7}{3}$
Or using both $A$ and $B$:
$C=A+B-\left(\frac{A}{3}\right)$

Let us apply this ratio $3:5:7$ to Row 3:
The first number is 12, and the second is 20.
Let us find the common factor:
$\frac{12}{3}=4$
$\frac{20}{5}=4$
Since the common multiplier is 4, the third number must be:
$7\times 4=28$

Thus, the missing number is 28.