1. ET -> SN -> SX -> FE -> FR -> TE -> TO -> ?

2. 0.00 -> 0.50 -> 2.30 -> 5.00 -> 8.20 -> 12.30 ->
17.30 -> ?

3. 11 -> 17 -> 23 -> 31 -> 41 -> 47 -> 59 -> ?

4. 365 -> 334 -> 306 -> 275 -> 245 -> 214 -> 184 -> ?

5. NÜD -> ZAY -> AKE -> UYO -> ALN -> ÞIR -> PMA ->
OYÝ -> ?

6. 1 -> 2 -> 6 -> 15 -> 31 -> 56 -> ?

7. 5 -> 25 -> 61 -> ? -> 181 -> 265

8. 0 -> 4 -> 18 -> 48 -> ? -> 180

9. 81, 9, 45 -> 64, 8, 36 -> ?, ?, ? -> 36, 6, 21