What number should replace the question mark?
12 - - - 25
5 - - - 11
21 - - - 43
18 - - - 37
2 - - - ?
5
12 x 2 + 1 = 25 5 x 2 + 1 = 11 21 x 2 + 1 = 43 18 x 2 + 1 = 37 2 x 2 + 1 = 5
5 11 6 9 13 18 11 20 21 25 16 ?
