there are two series in this puzzle,
First is 11,19,26,32,37 & second is 15,18,21,24

first series is AP with a decreasing difference
11 -> 19 => 8
19 -> 26 => 7
26 -> 32 => 6
32 -> 37 => 5
thus next number should be 37 + 4 => 41

second series is AP with a difference of 3
15, 18, 21, 24 => next number should be 27