15
11, -10, 9
23
There really is no way of telling, but my guess is 22.
There are some solutions where the sequence goes ... 14, 15, 13, ... but since yours goes ...,14, 1, 5, 13, ... it is not clear what the solution is.
15
11, -10, 9
21
23
The answer is 15 because the pattern is subtract one, add two
It is 129.
10,20,30,20
17?
There really is no way of telling, but my guess is 22.
15
The next number in the sequence is 15. The pattern is as follows: from 1 to 6 is +5, from 6 to 9 +4, from 9 to 12 +3, from 12 to 14 +2, and then from 14 to the answer (15) +1.
There are some solutions where the sequence goes ... 14, 15, 13, ... but since yours goes ...,14, 1, 5, 13, ... it is not clear what the solution is.