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4 - (2/5+7/18)

2 - (11/19+15/38)

5 - (2/5+5/14)

7 - (19/40+1/3)

4 - (2/5 + 7/18) = 3 19/90

1) 2/5 + 7/18 = 36/90 + 35/90 = 71/90

2) 4 - 71/90 = 3 19/90

2 - (11/19 + 15/38) = 1 1/38

1) 11/19 + 15/38 = 22/38 + 15/38 = 37/38

2) 2 - 37/38 = 1 1/38

5 - (2/5 + 5/14) = 4 17/70

1) 2/5 + 5/14 = 28/70 + 25/70 = 53/70

2) 5 - 53/70 = 4 17/70

7 - (19/40 + 1/3) = 6 23/120

1) 19/40 + 1/3 = 57/120 + 40/120 = 97/120

2) 7 - 97/120 = 6 23/120