which number best completes the sequence 1 1 3 2 4 6 5 25

[Carm]

Yeah, I messed up when I was working the problem

Cant get the second one though.
2 6 3 8 6 12
2+4=6-3=3+5=8-2=6+6=12-1=11
+4, -3,+5, -2,+6, -1 <-is this last number right?

¿Possible answers: 2, 15, 18, 32, 28¿

EDIT: mikebw. Looking at the problem. Its adding positive one to both the negative and positive number. So after 11 it would be 18
2+4=6-3=3+5=8-2=6+6=12-1=11+7=18
+4,-3,+5,-2,+6,-1,+7,0,+8,+1

+4+1=5
-3+1=-2

Carm