Условие:

8 + 17
6 + 28
4 + 39
63 − 8
30 − (6 + 6)
40 − (7 + 7)
50 − (8 + 8)
60 − (9 + 9)
62 + 30 − 2
20 + 75 + 5
83 − 60 + 7
72 − 40 + 8

8 + 17 = 8 + (7 + 10) = (8 + 7) + 10 = 15 + 10 = 25
 
6 + 28 = (4 + 2) + 28 = 4 + (2 + 28) = 4 + 30 = 34
 
4 + 39 = (3 + 1) + 39 = 3 + (1 + 39) = 3 + 40 = 43
 
63 − 8 = 63 − 3 − 5 = 60 − 5 = 55
 
30 − (6 + 6) = 30 − 12 = 30 − 10 − 2 = 20 − 2 = 18
 
40 − (7 + 7) = 40 − 14 = 40 − 10 − 4 = 30 − 4 = 26
 
50 − (8 + 8) = 50 − 16 = 50 − 10 − 6 = 40 − 6 = 34
 
60 − (9 + 9) = 60 − 18 = 60 − 10 − 8 = 50 − 8 = 42
 
62 + 30 − 2 = 2 + (60 + 30) − 2 = (2 − 2) + 90 = 0 + 90 = 90
 
20 + 75 + 5 = (20 + 70) + (5 + 5) = 90 + 10 = 100
 
83 − 60 + 7 = 3 + (80 − 60) + 7 = 20 + (3 + 7) = 20 + 10 = 30
 
72 − 40 + 8 = 2 + (70 − 40) + 8 = 30 + (2 + 8) = 30 + 10 = 40