54 - 24 : 6 + 40 = 54 - 4 + 40 = 50 + 40 = 90
90 - 21 + 42 : 7 = 90 - 21 + 6 = 75
35 - 30 : 5 + 25 = 35 - 6 + 25 = 29 + 25 = 54
54 - 24 : 6 + 40 = 54 - 4 + 40 = 50 + 40 = 90
90 - 21 + 42 : 7 = 90 - 21 + 6 = 75
35 - 30 : 5 + 25 = 35 - 6 + 25 = 29 + 25 = 54