1) 8 + 6 - 1 = 13
8 + (6 - 1) = 8 + 5 = 13
8 + 6 - 1 = 8 + (6 - 1)
2) 3 + 7 + 7 = 17
3 + (7 + 7) = 3 + 14 = 17
3 + 7 + 7 = 3 + (7 + 7)
3) 4 + 8 = 12
8 - 4 = 4
4 + 8 > 8 - 4
4) 7 + (9 + 1) = 7 + 10 = 17
(7 + 9) + 1 = 16 + 1 = 17
7 + (9 + 1) = (7 + 9) + 1