18 < X ≤ 20

16 < X ≤ 18

14 < X ≤ 16

12 < X ≤ 14

10 < X ≤ 12

8 < X ≤ 10

6 < X ≤ 8

4 < X ≤ 6

2 < X ≤ 4

0 < X ≤ 2