15 + 15 =
18 + 3 =
12 + 6 =
6 + 6 =
20 + 7 =
21 + 3 =
3 + 0 =
6 + 3 =
3 + 3 =
9 + 6 =
12
24
9
6
3
15
18
30
27
21