What comes next R, U, X, A,

25, ?, 87, 159, 269, 425 

What will come in place of the question mark (?) in the following series?

35, 38, 46, ?, 85, 120

What will come in place of the question mark (?) in the following number series?

124, 131, 117, ?, 110, 145

16, 20, 11, 27, ?, 38

24, 35, 57, 90, 134, ?

166        156       136      ?      66       16

38, 41, 50, ?, 158, 401 

4, 7, 12, 21, 36, ?

37, 49, 63, ?,  97, 117

What will come in place of the question mark (?) in the following series?

68, 76, 61, 85, ?, 98