pls answer it

21-22. 5, 10, 15, ____
Rule:_____

23-24. 2, 5, 8,____
Rule:_____

25-26. 3, 6, 9,____
Rule:_____

27-28. 1 , 4 , 9,____
Rule:_____

29-30. 20 , 24 , 28, ____
Rule:_____​