Study the given pattern carefully and select the number that can replace the question mark (?) in it.
First row: 21, 12, 19
Second row: 27, 10, 19
Third row: 24, 10, ?

(NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits.)

Let's determine the relationship between columns in each row:
First row: 21,12,19
Let's check the arithmetic combinations:

3
21+12×2
​
=
3
21+24
​
=
3
45
​
=15

=19
Let's try another logic:

(21−19)×6=12→2×6=12
Let's verify if this holds for the second row:

Second row: 27,10,19

(27−19)×something

=10
Let's try:

Row 1:21+12=33→33−14=19
Row 2:27+10=37→37−18=19
(No common pattern)

Let's examine column combinations:

Row 1:21+19=40⟹40−12=28
Let's check:

2×(Column 3)−Column 2=Column 1
Row 1:2×19−12=38−12=26

=21
Let's try:

3
Column 1+Column 2
​
+constant
Let's look at:

Row 1:
3
21
​
+12=7+12=19
Let's verify this rule:
3
Column 1
​
+Column 2=Column 3

Second row:

3
27
​
+10=9+10=19
This matches the third column exactly!

Third row: Applying this confirmed rule:

3
24
​
+10=8+10=18
Thus, the missing number is 18.