Guess what the next number in this sequence is:

16, 5, 14, 7, 21, 9, ____

To find the pattern in this sequence, we can look for any noticeable relationships or patterns between the numbers.

Upon inspection, we can see that the sequence alternates between adding and subtracting a value:

16 + (-11) = 5
5 + 9 = 14
14 + (-7) = 7
7 + 14 = 21
21 + (-12) = 9

Therefore, the pattern seems to be that odd-numbered terms in the sequence are obtained by subtracting a decreasing value (11, 7, 3), while even-numbered terms are obtained by adding an increasing value (9, 14, 19).

Following this pattern, the next number in the sequence would be obtained by subtracting a value of 3 from 9:

9 + (-3) = 6.

So, the missing number in the sequence is 6.