Условие:

8 + 9 + 4050
9 + 7 + 5020
8 + 8 + 3010
38 + 4060
54 + 2040
67 + 1030

8 + 9 + 4050 = 17 + 4050 = (7 + 10 + 40) − 50 = (7 + 50) − 50 = 7 + (5050) = 7 + 0 = 7
 
9 + 7 + 5020 = 16 + 5020 = 16 + (5020) = 16 + 30 = 6 + 10 + 30 = 6 + 40 = 46
 
8 + 8 + 3010 = 16 + 3010 = 16 + (3010) = 16 + 20 = 6 + 10 + 20 = 6 + 30 = 36
 
38 + 4060 = 8 + 30 + 4060 = 8 + 7060 = 8 + (7060) = 8 + 10 = 18
 
54 + 2040 = 4 + 50 + 2040 = 4 + 7040 = 4 + (7040) = 4 + 30 = 34
 
67 + 1030 = 7 + 60 + 1030 = 7 + 7030 = 7 + (7030) = 7 + 40 = 47