Find the missing term : 1, 0, 3, 2, 5, 6, ?, 12, 9, 20

The missing term is 7.

The sequence is a simple alternating addition and subtraction of 1 and 2.

1 + 1 = 2
2 – 2 = 0
0 + 3 = 3
3 – 2 = 1
1 + 5 = 6
6 – 2 = 4
4 + 7 = 11
11 – 2 = 9
9 + 10 = 20

Therefore, the missing term is 7.