Easy · Set 30

8 problems
1
Input: 4 → [?] → 8, what is the rule? =
2
Input: 7 → [?] → 21, what is the rule? =
3
Input: 2 → [?] → 7, what is the rule? =
4
? → [-1] → 9 =
5
Input: 7 → [+2] → ? =
6
Input: 4 → [×5] → ? =
7
Input: 3 → [-1] → ? =
8
Input: 10 → [?] → 30, what is the rule? =
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