1)
9 + 8 = 9 + 1 + ☐
8 + 5 = 8 + 2 + ☐
7 + 6 = 7 + ☐ + 3
9 + 7 = 9 + ☐ + 6
2)
7 + 4 = 3 + ☐
6 + 9 = 8 + ☐
4 + 9 = ☐ + 7
9 + 9 = ☐ + 9
9 + 8 = 9 + 1 + 7
8 + 5 = 8 + 2 + 3
7 + 6 = 7 + 3 + 3
9 + 7 = 9 + 1 + 6
7 + 4 = 3 + 8
6 + 9 = 8 + 7
4 + 9 = 6 + 7
9 + 9 = 9 + 9