Identify a pattern in the given list of numbers. Then use this pattern to find the next number.​ (More than one pattern might​ exist, so it is possible that there is more than one correct​ answer.)

The pattern is that each number is decreasing by 10. The next number would be 11.

The pattern in the given list of numbers is that each number decreases by 10.

To find the next number in the pattern, we subtract 10 from the last number in the list:
21 - 10 = 11

Therefore, the next number in the pattern is 11.