0 + 20 = 20
1 + 19 = 20
2 + 18 = 20
3 + 17= 20
4 + 16 = 20
5 + 15 = 20
6 + 14 = 20
7 + 13 = 20
8 + 12 = 20
9 + 11 = 20
10 + 10 = 20